Priority

We present the discovery of SMDET-1, a red, fast-moving object ($\mu \approx 1.3$"/yr) identified in time-resolved unWISE coadds using a pixel-level deep learning methodology called SMDET. Despite being relatively bright at 4.5 microns compared to many other recent WISE-based brown dwarf discoveries ($m_{[4.5]} \approx 14.6$ mag Vega), SMDET-1 had remained overlooked due to its location in a very crowded Galactic plane field ($b \approx 2.25^{\circ}$) and contamination from brighter background objects. SMDET-1 is also serendipitously detected at 4.5 microns in late-2012 Spitzer Deep GLIMPSE survey imaging. SMDET-1 is undetected in UKIDSS and Palomar/WIRC near-infrared imaging, with the strongest constraint on its temperature ($T_{\rm eff}$ < 391 K) arising from its Deep GLIMPSE color limit of $m_{[3.6]} - m_{[4.5]} > 2.81$ mag, which also implies a very nearby photometric distance < 7.4 pc. The Spitzer color bound corresponds to a Y dwarf phototype. SMDET-1 illustrates the importance of continued searches for nearby brown dwarfs within archival datasets like WISE and Spitzer, as well as the potential of pixel-level deep learning to discover astronomical moving objects that challenge traditional data analysis approaches.

The Hubble Space Telescope (HST) has advanced our knowledge of stellar evolution thanks to its unique high-spectral resolution and high-sensitivity capabilities in the UV region, especially for hot massive stars. Within the field of red supergiants (RSGs), it has led to several major insights as well, such as, for example, characterizing the embedded hot companion in the VV Cephei system, the detection of surface mass ejection from Betelgeuse, and unveiling the rich population of RSG+B binaries in the Magellanic Clouds. We demonstrate that nowadays (and in the decade to come) we need HST more than ever, as for the first time, thanks to the significant advances of high-angular-resolution interferometric and astrometric techniques, we can resolve the orbital motion of stellar components in RSG systems. However, the long wavelengths are dominated by the cool RSGs. Thus, observing such companions in the UV with HST is the only way to constrain the properties and velocity of the hot companions, adding the required missing piece of information for constraining the orbital solution and evolutionary status of RSG systems. Such observations are critical for understanding the interaction and mass transfer in massive binary systems and their connection to the observed population of supernovae.

Measurements of the thermal Sunyaev-Zel'dovich (tSZ) effect have yet to form a consistent picture of the thermodynamic state of the gas in the intracluster medium: their interpretation is complicated by foreground contamination and uncertain halo masses. We present new measurements of the tSZ effect around the Dark Energy Spectroscopic Instrument (DESI) Luminous Red Galaxy (LRG) sample, together with galaxy-galaxy lensing (GGL) measurements that enable a like-with-like comparison to state-of-the-art hydrodynamical simulations. We robustly isolate the tSZ signal by directly modeling the dust and radio emission of the target galaxies using the Atacama Cosmology Telescope (ACT) single-channel temperature maps, substantially reducing uncertainties from astrophysical foregrounds. Across halo masses $M_{500}=10^{13}-10^{14}~M_\odot$ and redshifts $0.4<z<1$, we find that the fiducial 1 Gpc$^3$ FLAMINGO simulation significantly overpredicts the observed tSZ signal at $\lesssim3'$ (i.e., $\lesssim 4\,R_{500}$ at $z=0.7$). Even the simulation with the strongest gas expulsion—which successfully reproduces the gas density inferred from kinetic SZ measurements of the same galaxy sample—overpredicts the thermal pressure. Because the strongest feedback model already reproduces the observed gas density, the remaining discrepancy is difficult to explain with additional gas depletion alone. Instead, current hydrodynamical simulations appear to overpredict the thermal pressure of galaxy groups by a factor of two, pointing toward missing non-thermal pressure support or significant departures from hydrostatic equilibrium.

The detection of Galactic double neutron stars (DNSs) through pulsar timing offers a unique opportunity to probe massive stellar and binary evolution. The observed DNS population exhibits an apparently bimodal eccentricity distribution, with an absence of systems at measured intermediate eccentricities, $0.4 \lesssim e_{\rm m} \lesssim 0.58$, whose origin remains unclear. We propose that this possible gap can arise naturally if the relationship between the progenitor masses and neutron star (NS) masses is non-monotonic, provided that the second-born NS receives a sufficiently small natal kick. We illustrate this scenario using the population synthesis code COMPAS, and find that our DNS population model can reproduce the observed orbital period-eccentricity distribution relatively well, including the apparent bimodality. Although a larger observed sample is required to draw more robust conclusions, our results suggest that this model provides a natural pathway for explaining current observations of Galactic DNSs through isolated binary evolution.

Chemical mixing during stellar mergers can significantly influence the subsequent evolution of the merger remnant. We perform a suite of three-dimensional hydrodynamical simulations of stellar mergers, each evolved for $\sim100$ stellar dynamical times until the remnant reaches a quasi-hydrostatic equilibrium. The simulations incorporate subgrid-scale diffusion models to capture the turbulent mixing of chemical elements. Starting with an idealized polytropic equation of state (EOS), we first identify the dominant mixing mechanisms and investigate how the merger outcome depends on the mass ratio, relative velocity, impact parameter, and stellar structure. We then extend our simulations to the context of stars embedded in active galactic nucleus (AGN) disks, using a realistic, composition-dependent EOS and AGN stellar models generated with the stellar evolution code MESA. We find that mergers with both younger metamorphic stars and H-rich accreting AGN stars can substantially rejuvenate old metamorphic stars through efficient core mixing after thermal relaxation. The merger remnants are nitrogen-enriched, with ${\rm N/O}\sim1$–3 and ${\rm N/C}\gtrsim5$, comparable to the abundances observed in the nebula surrounding SN 1987A. During subsequent stellar evolution, the remnants may converge onto the main sequence of isolated metamorphic AGN stars once they reach accretion–wind equilibrium. They may also deposit a significant amount of chemically enriched material into the AGN disk. This work provides a physical framework for connecting hydrodynamical stellar mergers with the long-term evolution of AGN stars and their observational and chemical signatures.

We investigate the impact of the vortex state of the ultralight dark matter (ULDM) on the dynamical friction acting on moving globular clusters. Comparing this force with that for the solitonic ground state, it is shown that the internal structure and rotation of the ULDM core strongly affect the orbital decay of globular clusters. In particular, co-directional rotation in a vortex state can lead to significant suppression of dynamic friction at certain distances where globular clusters and ULDM velocities match. Applying these findings to the Fornax dwarf galaxy, it is found that the Fornax timing problem is naturally alleviated.

We introduce a numerical technique to implement $N-$body realizations of axisymmetric and triaxial self-gravitating system starting from a spherical self-consistent models for which a phase-space distribution is known. The method is an improvement of the so-called adiabatic squeezing technique and allows one to have a better control of the effective ellipticities of the particle distribution and produces virialized systems that can be used as non-spherical initial conditions for $N-$body simulations. Some numerical stability tests are presented and discussed.

Supermassive black hole binaries are an inevitable outcome of hierarchical galaxy mergers, but their sub-parsec evolutionary phase between the kpc separations resolvable by direct imaging and the millihertz gravitational-wave regime targeted by LISA remains observationally elusive. Gravitational lensing of background stars by SMBH binaries has emerged as a powerful complement to periodic variability searches, periodic Doppler-boost signals, and circumbinary accretion hydrodynamic models. Two distinct lensing channels are reviewed: (i) the gravitational lensing of Milky Way bulge stars by the central Sgr A-star binary, whose secondary image is now within reach of ELT-class instruments; and (ii) the recently introduced Quasi-Periodic Lensing of Starlight (QPLS) mechanism, in which the rotation of caustics produced by a non-active SMBH binary magnifies individual bright stars in its host galaxy on the orbital period of the binary. The QPLS framework predicts 1-50 (190-5000) binaries per cubic parsec with periods below 10 yr and redshift z less than 0.3, opening a multimessenger window onto pulsar timing array sources and LISA-band events. After outlining the theoretical foundation, microlensing formalism, observational status, and the synergy with pulsar timing arrays and LISA, we identify outstanding challenges and project the field into the LSST era.

We present the first systematic search for electric vector position angle (EVPA) swings in the millimeter-wave (mm-wave) emission of blazars, using five years of observations from the South Pole Telescope SPT-3G camera at 95 and 150 GHz, and investigate their connection to gamma-ray flares. Of the 168 bright sources in the  1500 square degrees SPT-3G Main Field, eight have sufficient polarization signal-to-noise for reliable EVPA measurement, four of which have continuous Fermi LAT gamma-ray detections. We detect EVPA swings in all four gamma-ray-active blazars and in none of the remaining four, consistent with the established connection between EVPA swings and high-energy emission seen at optical wavelengths. The observed swing amplitudes and rotation rates are smaller than those found in optical studies, consistent with mm-wave EVPA variability being slower than at shorter wavelengths. Random walk simulations of the polarization angle using a multi-cell model fail to reproduce both the number, amplitude, and duration of the observed swings, suggesting that this mechanism is insufficient to explain the observed swing population. Analysis of EVPA variability on one-week timescales is consistent with the anti-correlation between polarization degree and EVPA rotation rate previously observed at optical wavelengths. Of the 14 detected swings, eight are within 30 days of a gamma-ray flare. While many individual swing-flare associations are found to have a very low probability of happening by chance, the full ensembles of 95 and 150 GHz swing time lags with respect to gamma-ray flares are found to be consistent with random coincidence.

The processes controlling the early mass growth of future massive stars remain poorly understood, particularly the connection of this growth to star clustering and hub-filament systems (HFSs). This connection is difficult to establish observationally, because projection effects and line-of-sight confusion in position-position-velocity (PPV) data can distort the information about the intrinsic filamentary structure. To investigate this connection, we used a three-dimensional magnetohydrodynamic (MHD) simulation of star formation, where stars are represented by accreting sink particles. We identify clustered stellar environments, reconstruct time-dependent accretion histories, and investigate the relation between enhanced-accretion episodes and the locations of HFSs. We also use line radiative transfer modeling to produce synthetic molecular-line observations and examine how the same structures appear in projected PPV data. In our simulation, we find that 80% of future massive stars are associated with clustered environments. Their growth is also highly episodic: typically, about 40% of the accreted mass is gained during periods of enhanced accretion that occupy only about 10% of the total growth time. Periods of enhanced accretion occur slightly closer to three-dimensional HFS proxies, suggesting a possible link between HFS morphology and episodic accretion in future massive stars. Overall, our results suggest that the early growth of future massive stars is connected to both their clustered environment and the HFS structure of the surrounding gas, and projection effects must be considered when interpreting HFS in PPV data.

The spatial distribution of metals in the intracluster medium (ICM) is a sensitive tracer of the chemical and dynamical history of galaxy clusters. While most cool-core (CC) clusters exhibit a centrally peaked Fe abundance profile, several outliers show an anomalous central Fe drop, potentially associated with the AGN activities. We revisit the reported large-scale (sim 100 kpc) central Fe drop in the massive CC cluster MACS J1931.8-2634 using new XMM-Newton observations. We aim to verify this feature and search for imprints of AGN feedback on the ICM metallicity distribution. We analyzed sim 170 ks of new XMM-Newton observations and re-analyzed sim 100 ks archived Chandra observations. We derived radial and two-dimensional (2D) Fe abundance maps from CCD spectra. High-resolution RGS spectra were used to constrain the Ne/Fe abundance ratio to test the dust depletion scenario. Spectral fitting was performed in SPEX using an updated atomic database and both single- and multi-temperature collisional ionization equilibrium models. The previously reported central Fe drop is not confirmed in the radial profile from XMM-Newton. However, the 2D Fe distribution is clearly asymmetric: Fe-rich regions are elongated along the axis of the AGN cavities, extending beyond their immediate scale. The Ne/Fe ratio in the core is consistent with solar (${\rm Ne/Fe} = 1.03^{+0.25}_{-0.23}$), arguing against the dust depletion scenario.

The outskirts of galaxies show their beauty by an assembly of Globular Clusters and satellite galaxies, but also by interactions with their environment. Galaxies in clusters experience dynamical effects by mutual encounters and by the intra-cluster gas. This latter exerts a drag to remove gas from the outskirts. These stripped clouds are capable to form stars and open fundamental questions on astrophysical processes, as e.g. the survival of intergalactic clouds, the star-formation process, the evolution of isolated star clusters, etc. Our studies target at star clusters around the Virgo cluster spiral galaxy NGC 4254, observed within the VESTIGE survey. 60 young clusters are identified in the GALEX/FUV with different masses, ages, and separations from the mature galactic disk. Only half of them are also emitting H-alpha as long as the clusters are still encompassed by gas until ram pressure strips it off leading to star-formation quenching and LyC escape.

Standard frequency-domain searches for quasi-periodic oscillations (QPOs) in active galactic nuclei generally assume sinusoidal variability. However, $\gamma$-ray blazar emission often shows asymmetric flares and localized bursts, causing spectral leakage that can reduce the sensitivity of conventional methods to non-sinusoidal periodic signals. We analyze a blind sample of 100 high-cadence (7-day binned) Fermi-LAT blazar light curves. After baseline detrending with Singular Spectrum Analysis, we apply the Fast Template Periodogram using three template families: a sinusoid, a Gaussian burst, and an empirical asymmetric template derived from PG 1553+113. Candidate signals are then evaluated with a Random Forest classifier trained on $5\times10^4$ simulated light curves to distinguish genuine periodic phase structure from stochastic red noise. We identify nine $>3\sigma$ periodicity candidates. Three persistent QPOs, including PG 1553+113, are recovered by all template models, whereas six additional candidates are strongly suppressed under the standard sinusoidal assumption but become detectable with morphology-aware templates. Machine learning validation rejects five of these as lacking stable phase coherence. The remaining candidate, PKS 1424$-$418, shows a structurally stable 4.8-year periodicity with a source-specific significance of $3.76\sigma$ (approximately $2.4\sigma$ after accounting for the trial factor of the 100-source sample). These results demonstrate that morphology-aware periodograms, combined with structural machine learning validation, improve the detection of burst-dominated QPOs that are difficult to identify with traditional harmonic searches.

Most of the Milky Way's predicted stellar-mass black holes remain hidden, especially at high Galactic latitudes or in the Galactic halo, where traditional dense-field stellar microlensing is ineffective. We propose an alternative method to map this isolated population via the spectral microlensing of compact, extragalactic H II regions. Projected onto the source plane, the physical Einstein radius of a Galactic black hole can match the typical core sizes of H II regions in distant galaxies. Microlensing triggers an achromatic magnification, producing distinct narrow emission-line excesses in integrated galaxy spectra. Because gravitational lensing is wavelength-independent, intrinsic line ratios are preserved, offering a robust discriminant against false-positive astrophysical transients. Notably, the efficiency of this method depends critically on the size of the H II regions: while extended regions suffer from low optical depth, compact regions with a physical size $\lesssim 10$ pc offer significantly higher magnifications. These compact cores, however, are heavily dust-obscured at optical wavelengths, making infrared and radio observations the primary windows for this method. Even so, the spatial sparseness of background H II regions and the stringent alignment requirement for high magnification limit the expected event rate to $\sim 10^{-6}$ per year. Nevertheless, this method offers a unique opportunity to detect stellar-mass black holes and constrain their abundance in such low-density environments.

We present a new suite of numerical simulations of Type II supernovae (SNe) detonating in Giant Molecular Clouds with a variety of density structures shaped by photoionization feedback. Ionizing radiation sculpts cavities and channels that guide SN energy to emerge from the cloud as shock-driven blowouts, rather than as a coherent spherically expanding shell as assumed in most sub-grid SN models adopted in galaxy or cosmological simulations. We investigate how such outflows differ to the 1-D descriptions, and whether or not the perturbations induced by the blowouts are sensitive to the host cloud's structure. A channelling parameter $P_\mathrm{chnl}$ is introduced to characterise the cloud's porosity and boundness using the morphology of the ionized channels. Our results reveal that the outflow velocities, whilst consistently higher than that of the spherical blasts, are in fact rather independent of the porosity of its local environment. The total kinetic energy and momentum deposited also appear similar across all runs. What is most sensitive to $P_\mathrm{chnl}$ is the mass of the materials carried in the outflows and their migration distances. It implies that SNe exploding in compact clouds with distinctive channel structures may have more confined metal injection radii and shortened turbulent driving scales, which consequently lead to a clumpier interstellar medium with higher density and metallicity fluctuations. We argue that molecular cloud structures play an equally important role to SN rates and energy budgets in stellar feedback sub-grid modelling.

We combine imaging data from the HST, JWST, and ground-based millimeter facilities to investigate the correlation between star formation rate (SFR) and molecular gas at the  100 pc scale of HII regions in three nearby galaxies: NGC628, NGC5194 and NGC5236. The JWST 21 micron maps of the three galaxies offer a unique insight into the dust-absorbed SFR at high resolution. We find that the relation between the surface densities of SFR and molecular gas has a slope of  1.85, in log-log scale, significantly steeper than previous results for nearby galaxies but closer to the trends found for molecular clouds in the Milky Way. The steep relation also holds on larger,  500 pc, scales, and results from the high-resolution imaging that cleanly isolates the star-forming region emission from the underlying galaxy's diffuse contribution. The diffuse emission at 21 micron is, in fact, found to correlate with the galaxy's stellar mass. Comparisons with physical models of star formation are inconclusive; they overlap with the locus of the 100 pc data, but have difficulties in reproducing the data scatter. Possible exceptions are models that add a power law tail to the gas density probability distribution, due to the large range of free parameters allowed. We find that local HII regions, high redshift star-forming clumps, and low and high redshift starburst galaxies form a single sequence of star formation over three orders of magnitude in gas surface density.

Studying AGN pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive black hole fueling and feedback. We cross-match between the Big Multi-AGN Catalog (The Big MAC) and the public data archive of the VLT/MUSE, and obtain 12 AGN pair candidates in the local universe ($z\lesssim0.1$) with a projected distance $r_{\rm p}\leq 20\rm\,kpc$. Using the archival VLT/MUSE data, we present a spatially resolved study of the ionized gas kinematics and ionization properties of these 12 AGN pair candidates. By decomposing the optical emission lines into two Gaussian components, we try to separate gas associated with disk rotation from non-circular motions. We further identify dominant ionization mechanisms using spatially resolved BPT diagnostics. We find that both nuclei in 4 of the 12 systems are classified as Seyfert or LINER. In addition, three nuclei are classified as star-forming or composite in the optical diagnostics, but are identified as AGNs at other wavelengths. Kinematically, regularly rotating ionized gas disks are detected in 16 of 24 nuclei. Prominent tidal features traced by ionized gas are also detected in 9 systems. Ionized gas outflows are widespread and are detected in 18 nuclei. Finally, for three nuclei (Mrk 739A, NGC 7592B, and J1544+0446A), we find evidence for fading AGN activity over the past several $10^{4}\rm\, yr$, based on optical emission-line ratios and an assumed AGN photoionization model.

Molecular bubbles are widely used as tracers of stellar feedback; yet, their identification in spectral-line surveys remains challenging because both cavity morphology and kinematic structure must be assessed consistently in position–position–velocity (PPV) space. We present the Bubble-Weight Fields (BWFields) framework, a PPV-based method that for the first time enables the automated and objective identification and analysis of enclosed molecular bubbles directly from spectral-line data cubes. BWFields constructs a bubble-weight field, $W_{l,b,v}$, which encodes cumulative evidence for cavity interiors by aggregating topological signatures across multiple signal-to-noise tiers and velocity-integration scales. Contiguous cavity interiors are segmented as weight-clumps and associated with surrounding molecular gas, linking candidate bubbles to the structure of their host clouds. Shell morphology is characterized using radial intensity profiles and emission-defined intensity skeletons, which capture the shell geometry as traced by the observed emission. Bubble kinematics are quantified using azimuthally sampled position-velocity (PV) diagnostics, along with a turbulence-normalized expansion significance, which serves as a direct measure of the expansion-like velocity organisation. Applied to MWISP $^{13}$CO observations of the G17 region, BWFields identifies a population of bubble candidates with a broad range of morphologies and velocity structures in complex environments. BWFields establishes a scalable and physically interpretable framework for molecular-bubble studies in large surveys, enabling systematic investigations of stellar feedback in the Galactic interstellar medium.

Radio galaxies show a wide range of morphologies, from regular double-lobed systems to more complex and distorted radio structures. In this chapter, we focus on irregular radio morphologies, defined as sources in which the radio jets and lobes deviate from a straight and symmetric structure. Bent-tail radio galaxies and winged radio galaxies are two important examples of such sources. Bent-tail radio galaxies show curved jets or lobes, mainly shaped by the interaction between radio plasma and the dense intracluster or intragroup medium. Winged radio galaxies show faint off-axis emission, which may be related to plasma backflow, jet reorientation, episodic activity, galaxy mergers, or environmental asymmetry. The Square Kilometre Array (SKA) continuum surveys will provide the sensitivity, angular resolution, frequency coverage, and image quality required to identify and study large samples of such irregular radio galaxies. These data will make it possible to detect faint extended structures, including diffuse tails, weak bridges, remnant lobes, and low-surface-brightness wings. The identification and classification of these sources will require a combination of machine-learning methods, quantitative morphology measurements, multi-wavelength host-galaxy association, and expert visual inspection. The study of irregular radio galaxies with SKA data will help to connect radio morphology with host-galaxy properties, Active Galactic Nucleus (AGN) activity, jet power, and surrounding environment. Such studies will provide important insight into jet-environment interactions, AGN feedback, the dynamical state of galaxy groups and clusters, and the evolution of radio galaxies across cosmic time.

Reverberation mapping of active galactic nuclei provides one of the most direct probes of the geometry and kinematics of the broad-line region by measuring time delays between continuum and line variability. Modern RM surveys frequently suffer difficulties with lag measurements due to poor signal to noise and aliasing, whereby multimodal lag posterior distributions arise due to seasonal gaps in our data. These challenge the reliability of commonly used fitting tools such as JAVELIN, which can return a high rate of false positives. We implement a new lag measurement package, LITMUS, and introduce a new framework that uses Bayesian evidence to identify false positive lag measurements, as well as examine the question of how many AGN present detectable lags in high redshift industrial scale surveys like OzDES and SDSS. Our analysis differs from previous RM studies in six key respects: (i) our inference is robust to the previously under-diagnosed numerical component of aliasing, (ii) we use a consistent methodology for all sources, (iii) uncertainty in the underlying AGN variability is fully marginalised, (iv) lag significance is assessed via Bayesian model comparison rather than heuristic metrics, (v) false-positive rates are quantified by comparison against random-chance recoveries and (vi) we use marginal likelihoods to distinguish between sources where a lag is not detectable in our data and sources that show no evidence of reverberation. Applied to the OzDES sample, we find that previous RM studies are likely to have overestimated the confidence of recovered lags, and we find a stark contrast between a low reverberation percentage for the MgII line (3-28% depending on assumptions) and much higher percentages in the CIV and especially the H$\beta$ line, which is consistent with 100%. We also present a re-analysed set of lags from the OzDES sample with better quantified reliabilities

SDSS J0225+0030 and SDSS J1723+5504 are two turn-on changing-look active galactic nuclei (CL AGNs) with transition timescales shorter than one year. Such short timescales pose a challenge for the current physical models of CL AGNs. We investigate this issue by exploring two possible mechanisms in this work. First, we consider the effect of a large-scale magnetic field on the viscous timescale, which can increase the radial velocity of the accretion disk. However, it is found that the timescale given by this model remains significantly longer than one year. Second, we improve the model of \citet{2025ApJ...988..207L}, which proposed that the inner thin disk in the bright state may form through the collapse of an advection-dominated accretion flow (ADAF) in the dim state, rather than being replaced by the advection of the outer thin disk. We re-estimate the transition radius $R_{\rm tr}$ between the inner ADAF and the outer thin disk through the observed variation of optical flux between the bright state and dim state. It is found that $R_{\rm tr}$ can be significantly reduced in these two objects owing to the lower gas temperature in the inner disk region (of the order of $10^4$ K), resulting from their large black hole masses ($\sim 10^9 M_{\odot}$) and small Eddington-scaled mass accretion rates ($\sim 0.01$). The cooling timescales given by the revised model in these two objects are found to be comparable to the observed transition timescales.

We report the first detection of TiO in star-forming regions based on Atacama Large Millimeter/submillimeter Array observations of Orion Source I, a well-characterized massive protostar. Multiple rotational transitions are identified, with emission spatially resolved within $\sim 50$ au, showing a compact distribution with a velocity structure consistent with the base of a rotating outflow. The spatial and velocity distributions of TiO are consistent with those of AlO, with both species being key dust seeding refractory molecules. \textbf{The column density of TiO is derived to be $(3.0 \pm 0.4)\times10^{15}\ {\rm cm^{-2}}$, corresponding to $X_{\rm TiO/SiO} \sim 12.8 \pm 1.7 \times10^{-3}$, higher than CI chondrites and indicative of efficient dust-to-gas conversion near the protostar.} We also identify a tentative detection of AlOH, which exhibits a more extended distribution along the disk surface, possibly indicating different conditions from those traced by TiO and AlO. The detection of TiO, a key dust seeding species, offers important constraints on refractory chemistry and the formation environments of primitive minerals, linking astrochemical processes in protostellar systems to the earliest stages of Solar System material formation.

Protostellar outflow shocks reshape local dust properties and molecular chemistry. The L1157 outflow is an archetypal chemically rich shocked region, but the thermal dust associated with its successive shocks has remained unresolved because molecular-line contamination obscures the broadband continuum. We obtained new James Clerk Maxwell Telescope (825–906 $\mu$m) spectral-line observations and Submillimeter Array (1.1–1.4 mm) continuum observations toward L1157 B0-B1-B2, probing spatial scales from 0.4 pc to 1200 au. After removing molecular-line contamination on a pixel-by-pixel basis, we derived the dust temperature, column density, and dust opacity index from continuum data spanning 70 $\mu$m to 1.3 mm. The line-corrected continuum maps reveal the dust distribution across successive shocks. The dust opacity index ($\beta\approx1.8$–2.3) indicates that grains have not grown to millimeter sizes throughout the shocked regions. Combined with previous $\rm NH_3$ observations, we find that the dust emission resolves into compact clumps along the precessing jet, whereas gaseous $\rm NH_3$ peaks at the shock fronts, reaching abundances of $\sim10^{-5}$ relative to $\rm H_2$, even where the 0.85 and 1.3 mm dust emission is detected at only 3–5$\sigma$. Our newly developed physicochemical shock model shows that $\rm NH_3$ forms predominantly on grain surfaces and is released by shock-induced sputtering, with the highest abundances occurring where post-shock re-adsorption remains inefficient. These results establish spatially resolved dust continuum imaging as a direct observational probe of grain evolution and provide new observational constraints on dust-gas interactions in protostellar shocks.

This work investigates the long-term evolution of the vertical structure of superthin galaxies within the framework of Milgromian dynamics (MOND). By constructing an observationally constrained model of UGC 7321, we test whether its disc can maintain an extremely flattened structure in a MOND gravitational field. We also construct models with different values of the MOND depth index $D_{\rm M}$ to study how the global MOND depth affects disc evolution. We perform three-dimensional hydrodynamical $N$-body simulations using the code Phantom of RAMSES. The evolution of the disc is quantified using $(h_z/R_{\rm D})$, Fourier amplitudes characterizing non-axisymmetric structures and vertical buckling, measures of vertical heating, and the vertical restoring force. In the observationally constrained model of UGC 7321, the galaxy develops a strong bar and undergoes a buckling instability during the early stages of the simulation. The bar strength then decreases, and the system eventually exhibits a weak bar structure. The stellar disc undergoes only limited vertical thickening, and most of the disc remains largely within the superthin regime, $h_z/R_{\rm D}<0.1$, after 5 Gyr. The comparison of models with different $D_{\rm M}$ values suggests that models with lower $D_{\rm M}$ values, associated in our model suite with higher baryonic masses or more compact discs, exhibit stronger vertical heating and more significant disc thickening. By contrast, models with higher $D_{\rm M}$ values, corresponding to lower masses or more diffuse structures, tend to maintain a superthin structure. Overall, the simulation results indicate that superthin discs can remain vertically thin during long-term isolated evolution in MOND, and that the long-term maintenance of superthin structures is influenced, at least partly, by the degree to which a galaxy lies in the low-acceleration regime.

We present spectral measurements for 17 Little Red Dots (LRDs) and 14 blue broad-line active galactic nuclei (AGNs) at $2\lesssim z \lesssim 6$ using multi-epoch JWST NIRSpec MSA spectra from the NEXUS program, sampling rest-frame timescales of $\sim 1-3$ months. Overall, the LRD population shows significantly enhanced Balmer decrement compared with both blue JWST AGNs at similar redshifts and 56 low-redshift broad-line AGNs matched in H$\rm\alpha$ luminosity. The rest-optical continua of LRDs show little ensemble variability (rms $\lesssim 3\%$), and the total H$\rm\alpha$ emission also shows weaker ensemble variability compared with low-redshift AGNs matched in H$\rm\alpha$ luminosity and rest-frame timescales. Based on the flux uncertainties, we constrain the intrinsic H$\rm\alpha$ rms variability to be $\lesssim 4\%$ for the LRD population over these timescales. Combining our results with recent broad-line variability measurements of LRDs over yearly to decade timescales reveals a low-level white-noise pattern across all timescales, in stark contrast to the variability amplitude ($\sim 6\%$ over monthly timescales) and red-noise pattern observed in normal AGNs. These results add to the growing observational studies that suggest population-wise, LRDs have weak variability both in optical continuum and broad-line emission. Furthermore, the distinct white-noise broad-line variability pattern suggests different production mechanisms of broad-line emission in LRDs as opposed to normal AGNs, and/or different properties of the driving ionizing flux from the central engine.

Stellar shells are low-surface-brightness structures that typically appear as concentric arcs. They are observed in many giant elliptical and lenticular galaxies, as well as in some spiral and dwarf galaxies. They presumably result from minor and intermediate close-to-radial mergers of galaxies. An essential factor in determining the merger time are the distances of shells from the centre of the galaxy. Consequently, estimates of the merger time can be significantly affected if some shells remain undetected due to projection effects. In this study, we present the first systematic investigation of how measured shell radii depend on the orientation of a galaxy relative to the observer. Using the Illustris TNG50 simulation, we examine shell galaxies from nine selected lines of sight and measure the shell radii. We model shell evolution and calculate the merger time accordingly for each viewing angle and quantify the impact of orientation on the inferred merger age. Our results indicate that the line of sight can have a substantial effect on merger-time estimates derived from shell radii.

We present the second data release (DR2) of the TNG50-SKIRT Atlas (TSA), a library of synthetic, spatially resolved galaxy observables. The atlas is constructed by post-processing a stellar-mass-complete ($10^{9.8}~{\text{M}}_\odot < M_\star < 10^{12}~{\text{M}}_\odot$) sample of 1154 $z=0$ galaxies from the TNG50 cosmological hydrodynamical simulation with the Monte Carlo radiative transfer code SKIRT. Compared to the first release, TSA DR2 extends the wavelength coverage from the ultraviolet to the submillimetre, including dust emission, and incorporates updated stellar population models together with an improved treatment of dust-enshrouded star-forming regions. The atlas provides spatially resolved spectral energy distributions, broadband images, and physical property maps for multiple viewing orientations, as well as a catalogue of integrated properties enabling direct comparison with unresolved observations. We validate the data products through extensive quality control, including an assessment of Monte Carlo noise, and demonstrate their internal consistency using diagnostic relations between luminosities and star formation rates. TSA DR2 provides a versatile resource for studies of dust attenuation and emission, star formation tracers, galaxy morphology, and multi-wavelength scaling relations across spatial scales. The atlas and associated data products are publicly released and are intended to support a wide range of observationally oriented studies of galaxy evolution.

Calcium is a highly depleted element in the interstellar medium (ISM), however its composition in the solid phase remains elusive. The detection of Ca-bearing dust has been limited due to its lack of distinct spectral features in the cold phase of the diffuse ISM. X-rays provide a direct method for exploring the absorption and scattering properties of interstellar dust. In this study, we utilize high-resolution X-ray absorption spectroscopy to characterize Ca-bearing dust analogs at the Ca K-edge using X-ray Absorption Fine Structure (XAFS). We present new X-ray absorption spectra of seven calcium-bearing interstellar dust analogs measured at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The extinction cross sections, calculated from the laboratory measurements are incorporated in the dust absorption model AMOL of the X-ray spectral fitting tool SPEX. We select three Low Mass X-ray Binaries (LMXBs) with high column densities, GX 340+00, GX 5-1, and GX 13+1, as background sources to study the intervening ISM along their sightlines. The best-fit models are compared with Chandra archive data using SPEX. Additionally, we employ simulations with the XRISM and NewAthena telescopes to achieve enhanced resolution and more effective coverage at the energy range near the Ca K-edge. These simulations set the boundary conditions for the future X-ray observation of calcium in the interstellar medium.

We present the environmental dependence of galaxy properties using $\sim$1.4 million BGS_BRIGHT galaxies in groups and clusters ($\log(M_h/M_\odot) \geq 12.5$) from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 at $0.05 < z < 0.55$. Using the magnitude-limited BGS_BRIGHT sample ($r < 19.5$) and the extended halo-based group catalogue, we examine how specific star formation rate (sSFR), Sersic index, and active galactic nucleus (AGN) fraction depend on halo mass across stellar masses $\log(M_*/M_\odot) = 9.0$-$12.0$ and halo masses $\log(M_h/M_\odot) = 12.5$-$15.0$. The median sSFR decreases with increasing halo mass, but much of this trend is driven by the rising satellite fraction rather than stronger suppression of individual galaxies. Satellites show lower median sSFR than centrals at fixed stellar mass and halo mass, most clearly at intermediate stellar masses. The stellar mass threshold at which the environmental trend becomes apparent shifts from $\log(M_*/M_\odot) \sim 11$ at $z \sim 0.4$ to $\sim 10$ at $z \sim 0.1$, a shift that partly tracks the survey's rising stellar-mass completeness limit. The mean Sersic index increases only weakly with halo mass (median $\Delta\log(n) \approx 0.05$ from field to cluster at fixed stellar mass and redshift). Among emission-line-detected galaxies (S/N $> 3$ in all four BPT lines), the combined AGN fraction increases monotonically with stellar mass. At fixed stellar mass, the Seyfert fraction shows no significant environmental trend (consistent with flat; field-to-cluster differences $\lesssim 3\sigma$ in the only well-populated high-mass bin), and the LINER fraction likewise shows no clear environmental trend. The most robust outcome of this work is the relative environmental ordering of galaxy properties and its decomposition into intrinsic suppression and compositional (satellite fraction) effects.

Ammonium salts may represent an important reservoir of volatile species in Solar system primitive bodies, but the question of how and when these salts can form during the star formation process remains unknown. In this paper, we use thermo-chemical models to study the formation of ammonium salts during the protoplanetary disk stage. We show that ammonium salts form efficiently in the inner disk midplane (i.e. $r \lesssim 50 $ au), inside the comet forming region. In this region, our model predicts that almost all the available nitrogen is in the form of salts (i.e. mainly in ammonium cyanate) at the surface of grains after evolving for 10 Myrs. For sulfur, we show that almost all the available S is in the form of ammonium hydrosulfide in the inner disk midplane. We show that inside $r\sim 30$ au, ammonium salt formation is enhanced by a cosmic-ray-driven sink effect that progressively converts gas-phase CO and N$_2$ into carbon dioxide and salts, respectively, at the surface of grains on a timescale $\gtrsim 1$ Myr. This impacts the location of the CO and N$_2$ radial snowlines which both shift closer to the star as a function of time.

Compton-thick Active Galactic Nuclei (AGN) represent one of the most elusive phases of massive black hole growth, yet are expected to contribute substantially to the Cosmic X-ray Background and the integrated growth of massive black holes. NGC 4945 is the closest Compton-thick AGN and amongst the brightest AGN in the hard X-ray sky, making it an important benchmark for more distant Compton-thick AGN. We present the first high-resolution X-ray spectral analysis of NGC 4945 using XRISM/Resolve. The entire 4-15 keV Resolve spectrum, including a strong Fe K$\alpha$ doublet and weak Compton Shoulder, is well described by a de-coupled dual-obscurer model. The model features a low-covering-factor Compton-thick primary obscurer intersecting the line-of-sight that permits the rapidly variable, direct transmitted coronal continuum to dominate above 10 keV. A Compton-thin secondary reprocessor with a high covering factor dominates the reprocessed emission between $\sim$4-10 keV. Assuming that virial motion accounts for line broadening, the secondary reprocessor can exist at $\sim$0.12 pc, and could help explain the weak high-ionisation optical and infrared emission lines observed in NGC 4945. If such obscuration geometries are common among more distant and/or fainter Compton-thick AGN, our results suggest that simpler coupled X-ray spectral modelling could substantially over-estimate Compton-thick covering factors and under-estimate intrinsic X-ray luminosities.

Open clusters are powerful tools for studying the Milky Way. While large spectroscopic surveys now provide spectra for many cluster members, automated pipelines and heterogeneous membership selections can introduce systematics and inflate apparent cluster scatter. Therefore, a homogeneous re-analysis with careful membership control and an explicit treatment of departures from Local Thermodynamic Equilibrium is valuable for establishing robust abundance gradients. The aim is to derive precise Galactic radial abundance gradients for multiple elements using open cluster giants, and to investigate how these gradients depend on cluster age. We re-analysed high-resolution infrared APOGEE Milky Way Mapper spectra from DR19 of the Sloan Digital Sky Survey for 655 open cluster members selected from Gaia data that satisfied strict quality cuts on signal-to-noise ratio. Stellar parameters and 18 elemental abundances were obtained using spectrum fitting with the Python version of Spectroscopy Made Easy, applying Non-Local Thermodynamic Equilibrium corrections for several key atomic species. Further quality control of the results was made by visual inspection of all fitted synthetic spectra. The metallicity of the clusters decreases with Galactocentric radius, following a global slope close to -0.06 dex/kpc. Beyond 10-11 kpc, there is modest flattening. In addition to the elements analysed in the \cite{otto2026} study, we derive open-cluster gradients for V, Cu, Zn and Yb using APOGEE spectra.

The Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM) is conducting an unprecedented wide-field integral field spectroscopic survey of the Milky Way, the Magellanic Clouds, and nearby galaxies using a strategy based on multiple dithered observations to achieve full spatial coverage, improved spatial sampling, and enhanced spectral depth. However, the scientific exploitation of these observations requires a robust methodology to combine the individual row-stacked spectra (RSS) into homogeneous three-dimensional data cubes. In this work, we present 3DCubeGen, a flexible and scalable reconstruction tool designed to combine multiple LVM dithers while preserving flux and propagating uncertainties. The method enables the coaddition of large datasets, improving the signal-to-noise ratio, enhancing spatial resolution, and increasing sensitivity to faint emission features, following and extending approaches previously implemented in integral field surveys such as CALIFA. We apply 3DCubeGen to a large set of LVM observations, including the Large and Small Magellanic Clouds and nearby galaxies, combining thousands of dithers corresponding to millions of spectra. The resulting data products demonstrate significant improvements in spatial sampling and spectral depth, enabling detailed studies of the ionised gas, stellar populations, and kinematics across extended regions. 3DCubeGen provides a robust and scalable solution for LVM data cube reconstruction and represents a key tool for exploiting the scientific potential of the SDSS-V Local Volume Mapper.

We present the discovery of Aquarius IV (Rubin J2201$-$0234) – the first ultra-faint Milky Way satellite to be identified using data from the Vera C. Rubin Observatory. This system was detected at $\sim$8$\sigma$ significance using Rubin Early Data Preview 2 (EDP2) photometry and independently confirmed at $\sim$6$\sigma$ significance in archival Dark Energy Camera imaging. Jointly fitting its morphology and distance, we find that Aquarius IV is a low-luminosity ($M_V=-1.9^{+0.6}_{-1.0}$), compact ($r_{1/2} = 19^{+4}_{-6}$ pc; $r_h = 0.60^{+0.14}_{-0.17}$ arcmin) stellar system in the outer Galactic halo ($D_{\odot} = 109^{+6}_{-8}\ \mathrm{kpc}$). Its stellar population is consistent with an ancient, metal-poor stellar isochrone ($\tau = 13$ Gyr, $Z=0.0001$). These properties closely resemble those of the smallest and faintest confirmed ultra-faint dwarf galaxies, though a globular cluster classification is not ruled out. Given the small number of detected member stars in Rubin EDP2, deeper imaging and spectroscopy will be critical for determining the properties and classification of Aquarius IV at higher confidence.

Cosmological simulations have recently begun to quantify the halo-to-halo variance in the phase-space distribution of dark matter around the Sun. We use a sample of nearly one hundred Milky Way-like galaxies from the TNG50 simulation to determine what aspects of this variance control the predictions for dark matter direct detection. Contrary to the isotropy assumed in the standard halo model, we find the dark matter median azimuthal velocity is nonzero and preferentially corotating, i.e., in the direction of the baryonic disk's rotation, ranging from 6-70 km/s (16th-84th percentile). This corotation suppresses predicted scattering rates in laboratory experiments searching for dark matter lighter than 50 GeV and significantly affects the expected daily modulation amplitude for directional detectors. In particular, this induces a 21% uncertainty on the upper limit of the dark matter-nucleon interaction cross section at peak sensitivity for a typical isotropic ton-scale experiment. This uncertainty is not irreducible, however: it is strongly correlated with the rotational velocity. If studies of the Milky Way's formation history determine the rotation speed, this astrophysical uncertainty is reduced to 7%.

We investigate how sub-sonic compressible magnetohydrodynamic (MHD) turbulence properties that are relevant for cosmic-ray (CR) transport in the Galaxy are affected by the nature and amplitude of initial fluctuations, and by the plasma compressibility $\beta$. We perform 3D simulations of decaying compressible ideal-MHD turbulence at $1024^3$ resolution with the PLUTO code. The level of density fluctuations in fully developed turbulence is insensitive to whether this state is reached starting from Alfvénic or fast-magnetosonic perturbations. Fast-magnetosonic injection is characterized by an early phase of rapid shock dissipation, followed by a turbulence-dominated decay with a rate comparable to that of the Alfvénic case. The contribution of fast-magnetosonic fluctuations in fully developed turbulence remains relevant only when the initial injection consists exclusively of fast modes. Large-amplitude turbulence ($\delta B/B_0>1$) is characterized by a nearly isotropic Kolmogorov or Iroshnikov-Kraichnan spectrum for Alfvénic or fast-magnetosonic injection, respectively. At low amplitudes ($\delta B/B_0\ll1$), both initial Alfvénic and mixed-wave perturbations lead to strongly anisotropic turbulence with spectra $\propto k_\perp^{-5/3}$ and $\propto k_z^{-2}$ (becoming steeper at $\beta\gg1$), whereas fast-magnetosonic perturbations produce a turbulent state populated by shocks with a nearly isotropic $k^{-2}$ spectrum. Magnetic-field curvature and mirror structures are strongly sensitive to fluctuation amplitude and plasma $\beta$. The predicted -2.5 power-law scaling emerges only in the large-amplitude regime at high $\beta$. This work highlights that features of sub-sonic compressible MHD turbulence that may affect CR transport are sensitive to large-scale conditions and to the plasma $\beta$. Their effect on CR diffusion and field-line random walk is the object of Paper II.

We present a model for the power spectrum of the density field of galaxies weighted by their star formation rate. This weighting is relevant in line-intensity mapping (LIM) when the observed line luminosity is strongly correlated with star formation, as is the case for the H$\alpha$ line. Our model reproduces the measured power spectrum in the IllustrisTNG simulation to within a few per cent across all scales, with fitting parameters that have clear physical interpretations. On scales of tens of megaparsecs, the model accounts for the weighted non-linear bias of galaxies as well as halo exclusion (2-halo term). On smaller scales, it incorporates the weighted distribution of satellite galaxies within haloes (1-halo term). The random sampling of satellite galaxies introduces a galaxy shot noise term to the power spectrum on small scales, and their confinement to haloes introduces a halo shot noise term on large scales. Omitting satellite galaxies from the analysis results in an underestimation of both the large-scale bias and the mean intensity by approximately 30 per cent each at redshift 1.5. Assigning the intensity of satellites to the centre of their respective haloes affects the power spectrum on scales $k > 0.3$ h Mpc$^{-1}$. Our fitting function provides a well-motivated parametrisation that can be used to interpret data from upcoming LIM surveys.

Strong Ly$\alpha$ emission observed from galaxies when the Universe is expected to be highly neutral is thought to trace large ionized regions that facilitate the transmission of Ly$\alpha$ through the IGM. In this work, we use deep JWST Ly$\alpha$ spectroscopy to constrain the size of a candidate ionized bubble at $z\sim8.7$ in the EGS field, with a potential radius of $R_b=2$ physical Mpc (pMpc) or larger. We measure a photometric galaxy density and find that the volume is a factor of $\sim2.5-3.6$ overdense, suggesting that there may be a large population of galaxies capable of creating an $R_b\sim2$ pMpc bubble. Then, we infer the Ly$\alpha$ transmission through the IGM for galaxies in the EGS volume using our deep spectroscopy, finding $\mathcal{T}_\mathrm{IGM}=0.26_{-0.14}^{+0.25}$. This transmission is consistent with the average at $z\sim9$ and is mildly inconsistent with the transmission expected for an $R_b\sim2$ pMpc bubble ($\mathcal{T}_{\mathrm{IGM},2\mathrm{pMpc}}=0.53-0.63$), implying that such a large bubble is unlikely to be present. However, the photometric galaxy density in the EGS field is larger than in several other deep fields. This overdensity and the moderate Ly$\alpha$ transmission may be consistent with smaller, $R_b\sim0.5-1$ pMpc bubbles in EGS. This additionally motivates the need for future wider area Ly$\alpha$ spectroscopy in EGS and other fields to obtain a more representative understanding of the sizes of ionized bubbles in the early stages of reionization, and the properties of the galaxies that create them.

The dynamics of globular clusters in the Fornax dwarf galaxy pose a challenge for the standard cold dark matter and can be used to test other models of dark matter. We study this dynamics in the context of an ultralight bosonic dark matter model, accounting for the damping term in a generalized Gross-Pitaevskii equation. Employing analytic formulas for the dynamical friction force, the infall time and evolution of globular clusters are compared in the cases with and without the damping term. It is argued that the damping term plays an important role in the Fornax timing problem in ultralight dark matter (ULDM) models. We found that the ULDM model with repulsive self-interaction can solve the Fornax timing problem in the absence of or with very small self-interaction, even if the initial position of the globular cluster is not far from the center of the galaxy. Still, the problem is resolved for strongly interacting repulsive ULDM, even for the most pressing case of globular cluster GC3, if its starting position exceeds 1.5 kpc.

We investigate the correlations of CO (2-1) emission (${I_{\rm CO}}$) with PAH (${I_{\rm F770W, PAH}}$ and ${I_{\rm F1130W}}$) and dust (${I_{\rm F2100W}}$) emission down to scales of $\lesssim$ 100 pc, by applying ${\tt raddest}$, a novel regression technique recently developed by T. Jing & C. Li (2025) that effectively handles uncertainties and outliers in datasets, to 19 nearby star-forming galaxies in the PHANGS sample. We find that for the majority of the data points in all galaxies, the scaling of ${I_{\rm CO}}$ with ${I_{\rm F770W, PAH}}$, ${I_{\rm F1130W}}$, and ${I_{\rm F2100W}}$ can be well described by log-log linear relations, though with substantial dependence on ionization conditions (i.e., HII-like, composite-like, and AGN-like). Under given ionization conditions, significant galaxy-to-galaxy variations are identified, and are primarily attributed to variations of intercept $b$, which exhibits clear bimodality. This bimodality is related to the normalized overall host galaxy star formation rate, such as specific star formation and star formation efficiency. The differences in slope $k$ and intrinsic scatter $\sigma$ across different MIR bands (${I_{\rm F770W, PAH}}$, ${I_{\rm F1130W}}$, and ${I_{\rm F2100W}}$) are minor compared to their galaxy-to-galaxy variations. All parameters ($k$, $b$, and $\sigma$) depend on the spatial scale of measurement, suggesting that the coupling among CO, PAH, and dust is regulated by different mechanisms at varying scales. We identify deviations from the log-log linear relation in the brightest regions, primarily characterized by a flattening of the slope. No significant (3$\sigma$) correlations are found between global properties and the best-fit parameters. We discuss the comparison to previous studies and plausible physics behind the statistical results obtained in this work.

Recently, Goldman (2024) obtained evidence for a large scale compressible, Burgers turbulence in the ism of a gravitationally lensed, star-forming galaxy at $z = 1.87$, with an outflowing wind. The turbulent timescale on the largest spatial scale has been found to be  500 Myr . This together with the large spatial scale of  6.4 kpc suggest a large scale generating mechanism (such as tidal interaction or merger) that lasted for  500 Myr. On the other hand, the outflowing wind is much younger and is probably the result of the intense star formation. Therefore, could it be that the star formation drives also turbulence on small scales? In the present work we utilize multi-point second order structure functions to find whether there exists also a small scale turbulence in this galaxy, and if so, try to identify its drivers. We obtained evidence for small scale turbulence whose largest spatial scale  240 pc for the nebular gas velocity field and   290 pc$ for the outflowing wind velocity field. These values suggest that stellar sub clumps or giant star clusters with an high concentration of young massive stars could be responsible for both the outflow and for the small scale turbulence.

Understanding dwarf galaxy formation is crucial for testing dark matter models and reionization physics. However, constructing stellar-mass complete spectroscopic samples at low masses is increasingly difficult, and the potential existence of a local void complicates studies in an average environment. The Photometric object Around Cosmic webs (PAC) method, which combines deep photometric and spectroscopic data to measure the excess surface density $\bar{n}_2w_{\rm{p}}(r_{\rm{p}})$ of photometric objects around spectroscopic tracers, offers a promising path forward. We model 349 $\bar{n}_2w_{\rm{p}}(r_{\rm{p}})$ measurements from DESI Y1 BGS and DECaLS, reaching $M_*=10^{6.4}\,{\rm M}_{\odot}$, using a stellar mass-halo mass relation (SHMR)-based subhalo abundance matching framework applied to two high-resolution $N$-body simulations from the Jiutian suite. The resulting SHMR is constrained down to $M_{\rm h}\simeq10^{8.0}\,h^{-1}{\rm M}_{\odot}$, revealing a clear upturn at $\sim10^{10.0}\,h^{-1}{\rm M}_{\odot}$ toward lower masses, indicating rising star-formation efficiency (SFE) in small haloes. This feature persists under extensions of the model that allow mass-dependent scatter, reionization-induced suppression of the halo occupation fraction, galaxy assembly bias, and alternative cosmologies. Combining with the results from Paper I, we find that central red galaxies dominate the low-mass regime. Our results motivate a hypothesis in which SFE is significantly higher than previously thought prior to reionization, enabling relatively massive galaxies to form in small haloes. These systems are subsequently quenched by the UV background, producing the central red dwarf galaxies observed. Finally, we obtain $3\sigma$ and $5\sigma$ upper mass bounds of $10^{8.80}\,h^{-1}{\rm M}_{\odot}$ and $10^{10.24}\,h^{-1}{\rm M}_{\odot}$ on the smallest haloes required to exist.

Several Lyman-alpha (Ly$\alpha$) emitters deep into the reionization era exhibit double-peaked Ly$\alpha$ emission profiles, raising the question of how the intergalactic medium can transmit photons blueward of the Ly$\alpha$ resonance at such high redshifts. To investigate this, we compute Ly$\alpha$ transmission along sightlines originating from galaxies in the Cosmic Dawn III simulation and identify cases that closely reproduce the observed double-peaked emission. In these cases, the sightlines intersect highly underdense voids located a few comoving megaparsecs from the source galaxy. These voids allow photons emitted blueward of Ly$\alpha$ to redshift through resonance without scattering while traversing them. The low opacity arises because the neutral hydrogen density scales with the square of the underlying gas density under ionization equilibrium, making sufficiently underdense regions with $\lesssim30~\%$ of cosmic mean density highly transmissive. Such voids naturally occur in the fluctuating cosmic density field, even in the vicinity of galaxies, and can also be associated with transmissive spikes in the Ly$\alpha$ forest. We find that the global probability of observing double-peaked emission is $\sim0.5~\%$ during reionization at an 80\% global ionization fraction, while no cases are found at 60\% ionization. We also find that this probability depends sensitively on the local ionizing background intensity, increasing by a factor of $\sim10^3$ for a tenfold increase in intensity. Recent accretion episodes of supermassive black holes can further increase this probability. These results suggest that double-peaked Ly$\alpha$ emission in high-$z$ galaxies can serve as a sensitive probe of the ionizing background during the late stages of cosmic reionization.

Understanding how galaxies and active galactic nuclei (AGN) jointly drive the reionization of the intergalactic medium (IGM) across cosmic time remains a major challenge in cosmology. We present Lumina, a large-volume radiation-hydrodynamic simulation that self-consistently follows the coupled evolution of the intergalactic medium, galaxies, and AGN through HI, HeI, and HeII reionization down to redshift $z=3$. Lumina evolves a cosmological volume of comoving side length $L_{\mathrm{box}}=500\,\mathrm{cMpc}$ with $2\times 6000^{3}$ resolution elements, corresponding to baryonic and dark-matter mass resolutions of $3.6\times 10^{6}\,\text{M}_{\odot}$ and $1.9\times 10^{7}\,\text{M}_{\odot}$, respectively. The simulation uses the moving-mesh code AREPO, combining the IllustrisTNG galaxy-formation model with a GPU-accelerated M1 radiation-transport solver in six frequency bins. The initial conditions employ separate transfer functions for baryons and dark matter and include their relative streaming velocity. Lumina predicts a late, predominantly stellar-driven hydrogen reionization, with the median sub-volume fully ionized by $z\approx 5.2$ and residual neutral HI patches persisting until $z\approx 4.75$. HeII reionization is driven self-consistently by AGN and is nearly complete by $z=3$. The simulation yields a Thomson-scattering optical depth in excellent agreement with Planck, an IGM thermal history and photoionization background broadly consistent with observational constraints, and a clear late-time thermal boost associated with HeII reionization. Its galaxy population remains consistent with the original IllustrisTNG project, while the larger volume improves statistics for rare objects, large-scale environments, and cosmic variance, enabling forward modelling of observables linking HI and HeII topologies to the evolving galaxy and AGN populations.

We present an information-theoretic analysis of the Cosmic Web that goes beyond the scalar density contrast and exploits the full structure of the tidal deformation tensor. The three eigenvalues ($\lambda_1, \lambda_2, \lambda_3$) of the tidal Hessian furnish a natural morphological classifier: clusters, filaments, walls, and voids correspond to (+,+,+), (+,+,-), (+,-,-), and (-,-,-) sign patterns, and their joint probability distribution function (PDF), known analytically in the linear regime from Doroshkevich (1970), defines a continuous Shannon entropy that quantifies the information encoded in the geometry of large-scale structure. Additional information resides in the shear invariants ${\cal Q} = {\rm Tr}(T^2)$ and ${\cal A} = {\rm Tr}(T^3)$, independent of the density. We derive the {\it Log-Doroshkevich distribution}, and show the $\mathbb{Z}_2$ symmetry survives the nonlinear map, broken only in matter fractions. Gravitational collapse breaks it through the density skewness: an Edgeworth treatment gives the cluster–void asymmetry $\mathcal{R}_{\rm cv}-1=0.609\,\varepsilon_3$ and entropy difference $\Delta H_{\rm CV}=0.107\,\varepsilon_3$ bits, with $\varepsilon_3=S_3^{\rm tot}(R)\,\sigma_0(R)\,D(z)$. The total skewness combines a gravitational term $S_3^{\rm grav}=34/7+n_{\rm eff}(R)$ and a primordial one $S_3^{\rm PNG}=S_3^{(1)}(R)\,f_{\rm NL}$ with $S_3^{(1)}(8\,h^{-1}{\rm Mpc})\simeq3\times10^{-4}$, smaller by four to five orders of magnitude, so the one-point asymmetry is gravity-dominated and only weakly sensitive to $f_{\rm NL}$. The multifractal entropy rate obeys $\dot H_{\rm mf}(z)=-3f(z)/(1+z)$, a growth probe complementary to $f\sigma_8$.

Dust extinction and reddening greatly contribute to type Ia supernovae (SNe Ia) observed color and magnitude variations. The models used to describe the extinction probability density function (PDF) are often simplistic, which can negatively impact SN simulations and cosmology. We present an analysis of simulated SN Ia extinction in galaxies along realistic lines of sight and investigate the parameterization of its PDF, as well as its dependence on host properties. We employed SKIRT, a radiative transfer code, to simulate observations of SNe Ia in different environments and generate synthetic extinction distributions. To parameterize and fit these distributions, we used both the commonly assumed single-parameter exponential PDF and some of its two-parameter generalizations. We find that the standard exponential PDF does not adequately describe simulated SN extinction: It underestimates low-extinction events and overestimates high-extinction ones. 2D KS tests show significant differences between the simulated extinction distributions for SNe in different environments, which the exponential parameterization cannot properly distinguish. In contrast, the two-parameter PDFs parameterize SN extinction distributions more accurately across all simulated environments. Variations in host morphology or dust mass relate to variations in different PDF parameters, meaning that the two effects can effectively be disentangled. We conclude that the two-parameter Weibull or exponentiated exponential PDFs offer the best parameterizations of SN Ia extinction for a wide range of simulated environments. Analyzing observed SN colors from the literature and assuming a Gaussian distribution for the intrinsic component, we conclude that a two-parameter extinction PDF results in intrinsically redder SNe, with their mean intrinsic color shifted  2$\sigma$ in relation to the standard exponential extinction PDF.

We present a high-resolution hydrodynamical simulation of the formation and evolution of nuclear structures in a Milky Way-mass galaxy using the SMUGGLE multiphase ISM and stellar feedback model. The system naturally develops a bar of length $\approx5$ kpc in isolation, driving sustained gas inflows toward the center that lead to the formation of a nuclear stellar disk (NSD) and a nuclear star cluster (NSC). By considering only stars born after bar formation, we cleanly isolate the nuclear structures and recover a clear inside-out growth of the NSD. Consistent with observational studies, we find that stellar feedback induces repeated shocks that regulate the size of the nuclear gas disk and drive gas from its outer edge toward the NSC region. Over time, the NSD and NSC share similar mass growth and star formation histories, except during accretion of a massive star cluster with mass $\approx 3\times 10^{7}\Msun$, comparable to the most massive cluster observed near the NSC of NGC 4654. Our results suggest that both the evolutionary timescale of the bar (and thus of the NSD) and the accretion history of star clusters are essential for obtaining tighter scaling relations among nuclear structures and their host galaxies. Finally, our results favor a lower bulge mass for the Milky Way than in our model ($B/D\approx 0.045$) to explain the compact size of its nuclear disk.

Optical-to-near-infrared interstellar polarisation, induced by aligned dust grains, generally follows a convex wavelength dependence, known as the Serkowski relation. However, observations in the ultraviolet (UV) and at [mid-]infrared wavelengths have indicated that some of the spectra do not follow this relation. Specifically, about 25% show an excess in the degree of polarisation at mid-UV wavelengths ($\lambda^{-1} > 3\,\rm \mu m^{-1}$), referred to as the super-Serkowski polarisation. For this study, we re-examined both the Serkowski and super-Serkowski spectra based on the joint effect of paramagnetic relaxation, known as the Davis-Greenstein (DG) and radiative torque (RAT) alignment. We used the observational data for HD 30614, HD 204827, HD 37903 and HD 161056 to constrain our modelling. We examined two types of radiation fields: one derived from the scaled interstellar radiation field and the other originating from a B-type star. For the super-Serkowski spectra of HD 30614 and HD 204827, our model demonstrates that RAT alignment enhanced by radiation produced from a B-type star below the Lyman limit ($\lambda=912Å$) can reasonably explain the observations and that a combination with the DG alignments results in a better fit for $\lambda^{-1}\geq 5.5\,\rm \mu m^{-1}$. For the Serkowski spectra in HD 37903 and HD 161056, only the RAT alignment by itself under the typical interstellar radiation field above the Lyman limit, within a typical cold neutral medium, can account for the observed spectra, with a combination of a very inefficient DG alignment. The capacity of our model to predict the starlight polarisation spectrum from infrared to far-UV is thus a promising tool for interpreting future missions that observe spectrophotometry in the UV bands.

Gravitational collapse creates large amounts of kinetic energy that could potentially seed turbulence. If such turbulence were also suitable to initiate dynamo action, the resulting magnetic field would further modify the dynamics, especially on small length scales. However, a small-scale dynamo is believed to require vortical turbulence, whereas the collapse produces mainly irrotational motions, which may not be efficient for dynamo action. Here, we study the efficiency of vorticity production during a turbulent collapse. We use a barotropic equation of state, where pressure and density gradients are parallel, and no magnetic field, so that vorticity can only be produced by viscosity. Using direct numerical simulations of gravitational collapse, we show that, for the parameter space accessible to our numerical resolution, this effect is related to the initial irrotational turbulence and is not a consequence of the collapse. Vorticity production along with the associated small-scale dynamo action are still expected to occur for sufficiently large Reynolds numbers, but some of the earlier numerical evidence in the literature is now found to be the result of subgrid scale modeling and not reproduced in direct numerical simulations.

One of the biggest challenges for Cosmic Microwave Background (CMB) experiments comes from the uncertainty in instrument bandpass calibration. Uncertainties in bandpass can limit foreground removal and spectral fitting, which are critical for inflationary and galaxy cluster measurements. CMB experiments currently use Fourier Transform Spectrometers (FTSes) to measure instrument bandpasses. However, FTS systems are currently systematics-limited, so significant improvements in bandpass measurements require novel calibrators. To this end, we developed a Frequency-selectable Laser Source (FLS) calibrator, which uses a laser with adjustable frequency coupled to a system that allows for laser power attenuation. Following initial testing with the first FLS prototype, we developed an upgraded version of the calibrator with improved performance. We present the upgrades to the FLS calibrator, the characterization of the upgraded calibrator and new laser source, and plans for testing with microwave instruments in the field.

We present a comprehensive Exposure Time Calculator (ETC) developed for the Wide-field Spectroscopic Telescope (WST) concept. The WST, currently in its conceptual phase, is designed as a next-generation large spectroscopic survey facility featuring three complementary observing modes: an Integral Field Spectrograph (IFS) covering 370-930 nm at R of about 4800; a high-resolution Multi-Object Spectrograph (MOS-HR) with four bands at R of about 40000; and a low-resolution Multi-Object Spectrograph (MOS-LR) with four channels at R of about 3800-4900. The ETC simulates the complete photon-propagation path from astronomical source to detector, incorporating wavelength-dependent system throughput (telescope transmission, instrumental optics, detector quantum efficiency), accurate sky background via ESO SkyCalc integration, and a comprehensive noise treatment (photon noise, sky background, read-out noise, dark current). The computational core is implemented as the "pyetc_wst" Python library built on the MPDAF framework, supporting multiple target spectral energy distributions (stellar templates, blackbody, power-law, emission lines, and user-uploaded spectra with arbitrary redshift) and spatial morphologies (point sources and Sersic extended profiles). Four operational modes enable flexible exposure-time optimization. Full spectral outputs include wavelength-dependent signal-to-noise ratio (SNR), source and sky photon counts, noise decomposition by component, and simulated extracted spectra. An interactive web interface, together with a REST API and a command-line tool, complete the user experience and enable batch survey-design workflows.

Deformable mirrors (DMs) are a key component of coronagraph instruments performing adaptive optics on the ground, and for future space observatories such as HWO and Roman CGI. Here, they will be used as part of the wavefront sensing and control system to "dig a dark zone” - remove residual stellar light to create a high-contrast region in the focal plane where faint companions can be detected. To reach the deep contrasts needed to directly image cool or reflected light planets (<1e-8) accurate calibration of the DM actuator gain is essential as picometer differences between the expected and realized DM surface can significantly degrade dark zone (DZ) digging efficiency. This increases the overheads needed to achieve a DZ and critically places more stringent requirements on observatory stability. Furthermore, DM gain varies with actuator stroke, necessitating rapid, in situ gain map recalculations to maintain DZ digging efficiency over time. Zernike wavefront sensors (ZWFS) are well-suited for this task as they efficiently provide picometer-level sensitivity and will likely already be included on board as part of a low order wavefront sensor for HWO. Here we present results from the HiCAT testbed at STScI where we calibrated gain maps for our Boston Micromachines 952-actuator micro electromechanical (MEMS) DMs using both a Fizeau interferometer and a ZWFS to compare performance. With the ZWFS we compute a gain map using both local linear fits around a given DM solution, and present a formalism for deriving more complex quadratic solutions which are more computationally intensive, but accurate over most of the dynamic range of each actuator. We then use these techniques to calibrate the DMs on the HiCAT testbed and show increased DZ digging efficiency with the new gain map and better contrast performance moving from 14 to 16 bit control electronics as enabled by these calibrations.

After two decades of observations, pulsar timing array collaborations have reported strong evidence for a stochastic gravitational wave background, most likely sourced by an inspiraling population of supermassive black hole binaries. Because that population is finite, anisotropy in the background is inevitable, producing hotspots on the sky that track the loudest binaries. Building on the Fisher formalism for anisotropic backgrounds, we recast the directional Fisher information as effective sensitivity curves on the sky, distinguishing the radiometer and full-Fisher estimators, along with a sky-weighted curve that reduces the anisotropic sky to a single spectrum and recovers the standard isotropic curve in the isotropic limit. We implement five sky-decomposition bases: pixel, spherical harmonic, square-root spherical harmonic, radiometer, and principal-map. We demonstrate the framework on an IPTA-like pulsar timing array: characterizing the angular response, analyzing the Fisher structure, recovering injected anisotropic hotspots, and forecasting future-array sensitivity. The framework is released as an extension to the sensitivity software package hasasia.

The NASA-ASI mission Imaging X-ray Polarimeter Explorer (IXPE) firmly established X-ray polarimetry as a core observation pillar of high-energy astrophysics, alongside imaging, timing, and spectroscopy. While IXPE made groundbreaking discoveries in the 2$-$8 keV range on both point and extended X-ray sources, the Gas Pixel Detectors onboard IXPE demand substantial improvements to be ready for the next generation of imaging X-ray polarimeters. Here, we present the development of a detector prototype that can deliver the next generation of sensitive imaging X-ray polarimetry across the energy band of 2–30 keV. We use Ar/DME based gas volume to absorb X-rays by the photoelectric effect and a pixelated CMOS readout ASIC, Timepix3, with excellent timing capabilities to image the resulting photoelectron track in three dimensions. The Timepix3 is integrated with a multiplication stage called InGrid that enables single-primary-electron detection from the gas volume. The photoelectron track reconstructed in three dimensions increases the polarimetric sensitivity towards the lowest operable energies, and the deadtime-free operation of the ASIC facilitates the usage as a focal plane instrument on high-throughput X-ray mirrors. With this prototype, we demonstrate a low-medium-energy X-ray polarimeter with excellent timing and moderate spectral capabilities.

Radio astronomy and aviation safety systems occupy opposite ends of the signal-power spectrum, yet both depend on the same finite resource and are increasingly squeezed by commercial broadband wireless services. The two fields protect their receivers using separately derived, apparently incommensurable criteria: the ITU-R RA.769 detrimental-interference threshold for radio telescopes, and the radar-altimeter interference thresholds established by RTCA Special Committee 239 for the 5G C-band coexistence problem. We introduce a single coexistence-margin framework, M(f,d) = Pth(f) - Prx(f,d), and show both criteria to be special cases of it. We apply this framework to two case studies, the Karoo Radio Quiet Zone surrounding MeerKAT and SKA-Mid, and the global 5G C-band/altimeter dispute, showing that, despite unrelated regulatory histories, both converged on the same three-lever solution: guard-band separation, bounded exclusion zones, and receiver-side filtering, governed by mandatory coordination rather than static exclusion. We then show that interference-excision, beamforming, and statistical-calibration pipelines developed for radio interferometry are closely analogous to, and in several cases directly reusable for, operations required by ADS-B validation, phased-array radar clutter rejection, and predictive-maintenance anomaly detection. The unifying framework, and the finding that two independently-arising regulatory histories converge on the same design pattern, is this papers central contribution: M(f,d) has not, to our knowledge, been proposed before as a common formalism spanning these two protection regimes, and the toolkit mapping distinguishes genuine reuse from looser analogy. The result is a reusable design pattern and shared skills/infrastructure pipeline, applicable wherever a narrowband receiver must coexist with a growing broadband commercial neighbour.

The BICEP Array (BA) is the latest in the BICEP/ Keck series of experiments that aim to measure the polarization of the cosmic microwave background (CMB) with small aperture polarimeters located at the South Pole. To constrain the frequency response of these receivers, each detector is serially coupled to a band-pass filter (BPF). The electric circuits of these BPFs utilize series and shunt capacitors as well as series inductors, but critically do not include shunt inductors which simplifies fabrication. The filters are designed and simulated with Sonnet, and optimized for noise by considering loading from the atmosphere and the CMB. Multiple 220 GHz detector modules have had their frequency response measured at the South Pole. The 270 GHz detector modules have recently begun testing in a lab setting, and their performance in a BA receiver will be measured this winter.

A promising new architecture for extreme-precision radial velocity (EPRV) spectrographs, hunting for small-amplitude stellar Doppler shifts induced by orbiting planets, is to build diffraction-limited instruments by using single-mode fibers fed by an adaptive optics system. However, the target stars are partially resolved when observing at the diffraction limit, and the resulting RVs are expected to be affected by differential limb coupling (DLC), an effect where the red- and blue-shifted sides of the stellar disk are coupled unequally into the spectrograph, producing an RV error term on the order of m/s for nearby EPRV target stars for the upcoming HISPEC spectrograph for Keck II. We present our efforts to directly measure the RV shifts resulting from DLC for the first time, using the diffraction-limited spectrograph PARVI, in order to verify the expected behavior of DLC and subsequently develop mitigation strategies for HISPEC and other future instruments. We outline an observing strategy designed to produce DLC-induced RV shifts of hundreds of m/s, and describe the execution of this experiment with PARVI. We use these data to characterize the PARVI tip-tilt guide camera and its performance, and have begun analysis of the derived RVs, though this investigation has proven complicated since the RVs are deeply entangled with other instrumental and algorithmic effects.

Read noise in infrared sensor arrays remains a major obstacle for ground- and space-based astronomy. It has long been recognized that the upcoming extremely large telescopes cannot meet their full potential unless read noise is significantly improved, and it is also a prohibitive constraint on the Habitable Worlds Observatory, a space telescope with the goal of detection and characterization of nearby Earth-like exoplanets. The main strategy for lowering read noise is averaging through multiple non-destructive reads. However, this typically results in less noise reduction than the 1/$\sqrt{N}$ scaling predicted by theory. In this work, we show the poor averaging behavior can largely be explained by readout glow, photon emission from the sensor electronics that generates photoelectrons in the pixels during readout. Because glow accumulates with reads rather than averaging, this imposes a fundamental noise floor of \sigma_{\rm min}   1.5 sigma_RN^(1/2)G^(1/4). This limits averaging in HxRG-like sensors to about 2-3 e- of noise, and linear-mode avalanche photodiodes (LmAPDs) to about 0.5 e-. We present laboratory data using both sensor architectures, with the LmAPD following the predicted noise value to within 0.1 e- over two decades of averaging.

Renewed interest in lunar exploration is creating a growing population of poorly tracked cislunar objects, some of which will ultimately impact the Moon$^{1}$. The ultimate fate of rocket upper stages or failed mission payloads is often unknown and unplanned. Determining the origin and physical properties of such objects will become increasingly important as sustained lunar exploration places humans and infrastructure on the surface$^{2;3;4;5}$. Here we present a ground-based physical and dynamical characterization of 2025-010D, a Falcon 9 upper stage predicted to impact the lunar farside on 2026 August 05. Backward propagation of its orbit independently links the object to the “Ghost Riders in the Sky” launch, while visible and near-infrared spectroscopy distinguishes it from natural objects and reveals absorption bands consistent with spacecraft thermal control materials. Photometric lightcurves confirm its elongated shape and reveal an unexpected change of more than 8 s in its $\sim$7 min rotation period during observations. We predict an impact between Bell and Einstein craters at $\sim$2.4 km s$^{-1}$, producing a crater $\sim$40 m in diameter. Since its provenance is independently known, 2025-010D provides a benchmark for identifying and characterizing future cislunar objects of uncertain origin.

IRTF-ASM-1 has been functioning well since its first light in 2024. This adaptive secondary mirror (ASM) was primarily developed to be an on-sky demonstration of the new hybrid variable reluctance actuator technology at the NASA Infrared Telescope Facility (IRTF). However, due to its physical robustness and our previous demonstrations of sensitivity enhancements with the ASM, we are interested in using it to optimize telescope image quality on a nightly basis. This will directly benefit science observations. However, as IRTF does not currently have adaptive optics expertise, we have been developing the system to be used with minimal human intervention. We present our progress in developing software for active optics mode with IRTF-ASM-1 using the single conjugate, facility 2x2 Shack-Hartmann wavefront sensor Felix. We also present techniques for removing low-order, large amplitude non-common path aberrations between Felix and our science instruments.

All-sky surveys in the soft X-ray band are essential for detecting transient objects such as high-redshift gamma-ray bursts (GRBs), which provide key insights into the early universe. HiZ-GUNDAM is a future satellite mission designed to detect and localize high-redshift GRBs. Its wide-field X-ray monitor, EAGLE, combines Lobster Eye Optics with a pnCCD imaging detector operating in the 0.4-4 keV band. Because of limited satellite telemetry, full-frame pnCCD images cannot be downlinked, requiring onboard event selection. Charged particles in the space environment produce background events that can be misidentified as X-ray photons, degrading detection sensitivity and potentially triggering false alerts. In this study, we developed a pnCCD readout system and evaluated charged-particle rejection using conventional grade methods and a convolutional neural network (CNN). Performance was evaluated using X-ray events from an Fe-55 source and electron events from a Sr-90 beta source. The CNN reduced the misclassification rate from 10.2-11.9% for conventional grade methods to 3.1% while maintaining a high acceptance rate for X-ray events. The improvement is particularly pronounced at higher deposited energies, reflecting the CNN's ability to distinguish track-like particle events from X-ray events by capturing detailed spatial features of charge distributions. Comparison with a thin-depletion-layer CMOS sensor further indicates that the thicker depletion layer of the pnCCD enhances discrimination performance. These results demonstrate that CNN-based event classification can substantially reduce charged-particle contamination while maintaining high X-ray acceptance, making it a promising approach for onboard event selection in future pnCCD-based wide-field X-ray missions.

High-resolution spectroscopy, typically operating at resolving powers R greater or equal to 25,000, has matured into one of the primary techniques for characterising the atmospheres of extrasolar planets. The ability of HRS to resolve individual rotational-vibrational lines of molecular bands, combined with the large Doppler shifts experienced by close-in planets during their orbits, allows planetary signals to be separated from quasi-stationary telluric and stellar contamination. Since the pioneering detection of carbon monoxide in the transmission spectrum of HD 209458b, HRS has enabled the identification of more than a dozen chemical species, including H2O, CH4, HCN, TiO, VO, Na, K, Li, H-alpha, He I, Mg, Ca, V, Cr, Mn, Fe, Co, Ni, and Ti, in a wide variety of transiting, non-transiting and directly imaged exoplanets . In addition to chemical abundances, HRS constrains the vertical temperature structure through the pressure dependence of line depths, and reveals atmospheric dynamics through Doppler shifts and asymmetries imprinted on the planetary cross-correlation function. This review synthesises observational and methodological progress from the past fifteen years with a focus on how current and forthcoming high-resolution facilities HARPS, ESPRESSO, NIRPS, CARMENES, CRIRES+, SPIRou, GIANO, and ultimately the ANDES, METIS and HARMONI instruments on the Extremely Large Telescope are reshaping our empirical view of exoplanet atmospheres.

Pollux is a high-resolution spectrograph and spectropolarimeter (R from 65000 to 100000) covering a spectral range from 100 nm to 1750 nm, proposed by a European consortium to equip NASA s Habitable Worlds Observatory (HWO). This instrument aims to revolutionize the study of stellar and (exo)planetary systems, as well as cosmic ecosystems, by combining high spectral resolution, broad and simultaneous spectral coverage, temporal stability, and unique UV spectropolarimetric capabilities, thus opening a new parameter space for astrophysics.

The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) photon and high-energy particle fluxes from the host star, which are poorly constrained. To address this key gap in our understanding of atmospheric retention, we present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, a NASA Small Explorer concept proposed in 2026. ESCAPE employs extreme- and far-ultraviolet spectroscopy (80 - 1650 Ang) to provide the first comprehensive study of the stellar EUV history and stellar coronal mass ejection (CME) environments that control atmospheric mass-loss and determine the habitability of rocky exoplanets. This paper outlines both the primary science goals of the mission, the breadth of future general observer investigations, and a detailed design study of the mission's instrumentation. The ESCAPE instrument comprises a grazing incidence telescope that feeds multiple diffraction gratings and a photon-counting detector. We describe a demonstration of the Hettrick-Bowyer telescope, etched silicon diffraction gratings, the microchannel plate detector and housing, and gold and zirconium coatings. We present a STOP analysis that verifies ESCAPE's ability to meet its structural integrity, thermal stability, and optical performance requirements throughout the mission environment.

The Wide-field Spectroscopic Telescope (WST) is a proposed 12 m wide-field spectroscopic facility combining several multi-object spectrographs. It requires a yet unprecedented number of detectors. In this paper we present conceptual architecture for the detector controller and infrastructure required to operate a large number of detectors, potentially applicable to WST, focusing on the system-level, power distribution, and the associated data handling. We also consider how these elements may evolve over the expected development timeline of such a facility. Motivated by the scale of the problem, we outline a possible distributed detector-controller architecture, based on modular units placed close to the detectors and networked backend electronics.

Stellar spectroscopy is a robust technique for determining fundamental stellar parameters such as effective temperature, surface gravity and metallicity. Spectroscopy Made Easy (SME) has long served as a framework for spectral synthesis and parameter inference. In this paper, we introduce webSME, a web-based extension of the Python implementation of SME. webSME integrates enhancements including a non-local thermodynamic equilibrium abundance correction mode, a precomputed grid of synthetic spectra for robust determination of stellar parameters from large wavelength ranges (thousands of Angstroms wide), Markov Chain Monte Carlo sampling for uncertainty estimation, and support for recent reference abundance patterns. It enables efficient and user-friendly analysis of high-resolution spectra, making it suitable for a wide range of applications - from detailed abundance studies to education and outreach. We demonstrate the performance of webSME on synthetic and observed spectra, including benchmark stars, and validate its accuracy against classical SME-based analysis. The platform's ease of access and advanced capabilities position it as a powerful tool in the modern astrophysical toolkit.

Photonic integrated circuits (PICs) promise order-of-magnitude reductions in the size, weight and power (SWaP) of optical subsystems for astronomy, planetary and Earth-observation missions, yet no PIC-specific space-qualification standard exists. This paper consolidates the principal NASA and ESA qualification documents that apply, or can be tailored, to astrophotonic PICs — arrayed waveguide gratings, photonic lanterns, fibre Bragg gratings, and integrated beam combiners (ABCD, discrete beam combiners, nullers) for spectrographs and stellar interferometers. A master qualification table lists 19 standard test steps with applicable standards and EU/USA test facilities. Two reference mission profiles — a LEO smallsat demonstrator and an HWO-class Lagrange-2 flagship — yield a tailoring matrix, while a TRL-versus-test-coverage roadmap maps each activity onto the NASA/ESA readiness levels and review gates. A survey of UV/visible/near-infrared platforms relates spectral coverage, maturity and flight heritage, and a radiation-effects summary shows passive silica, Si3N4 and laser-written cores are essentially radiation-tolerant while active III–V and Ge devices carry the hardness burden. The central outcome is a seven-phase qualification template (PIC-SQT) with explicit TRL gates, exact test procedures and mission-class tailoring; we further identify qualification processes relevant to PICs that current standards do not cover, and document 40+ years of optical-fibre flight heritage.

The Black Hole Explorer (BHEX) is a next-generation space very-long-baseline interferometry (VLBI) mission concept that will extend existing ground-based millimeter/submillimeter VLBI arrays to space. The Japanese astronomical community has contributed to BHEX mission development through the BHEX Japan Consortium, established in 2023. This paper provides a high-level summary of progress in Japan since 2024, including the establishment of the Black Hole Explorer Working Group (BHEX WG) at the Institute of Space and Astronautical Science (ISAS), JAXA, to conduct the Japanese side of the Pre-Phase A mission studies. We outline recent advances in key instrument technologies, including concept design studies of a 4.5 K closed-cycle mechanical cryocooler and prototype development of an ultra-wideband 300 GHz Superconductor–Insulator–Superconductor (SIS) mixer for BHEX. We also describe ongoing upgrades to Japan's ground infrastructure to support 86 GHz observations with VERA and simultaneous 86+230 GHz observations with the Nobeyama 45 m Telescope.

Planets with orbital periods longer than a TESS sector produce a single transit, and no periodogram method can measure their period: with one transit, every trial period longer than the observing baseline fits the data identically. We show this is not a sensitivity limit but a structural one – across 16 confirmed single-transit planets, Box Least Squares returns a power spectrum that is numerically constant over 95% of its search grid, and widening that grid from 27 to 200 days changes the median error by -0.0 percentage points. Orbital period can instead be recovered from transit duration through Kepler's third law and transit geometry, requiring no search grid. A direct inversion of these equations underestimates the period in 14 of 15 targets with a median signed error of -69%, because assuming a central transit returns the shortest period consistent with an observed duration. A neural network trained to marginalise over the unobserved geometry removes this bias, reaching a median absolute error of 40.5% against Box Least Squares' 79.5%, with the true period inside the 1-sigma interval for 14 of 16 targets. For NGTS-38 b, whose 180.5 d period lies ten times beyond the longest contiguous span of its TESS sector, marginalising over the unobserved geometry recovers a posterior median of 190.7 d with the true period at the 47.8th percentile, against 18.5 d from Box Least Squares. Because equilibrium temperature scales as P^(-1/3), the resulting factor-8.8 period interval compresses to a factor-2.1 temperature interval: T_eq = 445 K with a 68% interval of 272-562 K, sufficient to place the planet relative to the habitable zone from a single observation.

Photometric calibration of digitized photographic plates is commonly modeled with separable magnitude-, color-, and position-dependent terms, but this separability can break down when image quality varies across the field in a magnitude-dependent way, leaving coupled spatial systematics in the residuals. We introduce a deep-learning calibration framework, the Multi-Feature Fused Network (MFF-Net), which takes instrumental magnitude, color, and pixel coordinates as input and learns a single nonlinear correction that jointly captures their coupled dependencies. Tests on 1{,}200 digitized Chinese plates show that MFF-Net consistently outperforms the MYX25 method (Ma et al. 2025), improving the 5th–95th percentile precision from 0.11–0.26 mag to 0.08–0.18 mag and delivering an approximately factor-of-two gain for bright sources. The learned correction largely removes the magnitude–position coupling seen in post-calibration residual maps, enabling higher-precision plate photometry and more reliable use of large historical plate archives.

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a $7^\circ$ angle of incidence that provides high reflection in the short-wavelength band, high transmission in the long-wavelength band, and a sharp cut-on near 550 nm. A multilayer thin-film design process was used to meet these spectral requirements while reducing polarization aberrations and chromatic WFE sensitivity. Reflected phase optimization was also incorporated to reduce sensitivity to manufacturing-induced layer-thickness variations, which can produce wavelength-dependent WFE and degrade coronagraph performance. The resulting coating-induced WFE was propagated through simulations of a vector vortex coronagraph to assess contrast performance. Simulations predict dark-hole contrast residuals at the $10^{-12}$ level, indicating that the optimized dichroic mirror does not limit coronagraph performance.

X-ray spectroscopic observations of the solar corona and flares provide crucial diagnostics of plasma properties and are essential for understanding the physical processes responsible for coronal heating and solar eruptive activity. The Chandrayaan-2 Solar X-ray Monitor (XSM) provides disk-integrated spectra of the Sun in the 1–15 keV soft X-ray band, enabling modeling of the thermal X-ray emission from the corona across quiet phases to intense solar flares. XSM has been operational for about seven years, starting from the last solar minimum and covering the maximum of the current Solar Cycle. The Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) instrument on board INSPIRESat-1 covers the solar X-ray spectra in a similar energy range as XSM and was operational during 2022–2026. With multiple instruments simultaneously observing the Sun in X-rays, there is scope to compare measurements across instruments. Here, we present the cross-calibration of XSM with DAXSS and a broadband X-ray flux monitor, the GOES-16 X-ray Sensor (XRS). Comparisons of XSM and DAXSS spectra reveal an unaccounted attenuation in the XSM low-energy response. Supported by laboratory measurements, we attribute this difference to the effective detector beryllium window thickness being 25 microns rather than the previously assumed 8 microns. Incorporating this revision into the XSM calibration significantly improves the agreement between the two instruments, with flux measurements agreeing within  10% in the 1–8 Angstrom band. Comparison with GOES-16 XRS measurements over a broad range of solar activity levels further demonstrates consistency, with a median flux difference of less than 10%.

We present the science motivation, preliminary design requirements, device laboratory testing and a prototype for an new experimental platform for solar observations, MiraSOL. MiraSOL will use digital micromirror technology to actively select regions on the solar disk for spectroscopic observation to determine the spatially dependent radial velocity signatures of stellar variability, and can create transits on the solar disk to probe the effects of stellar contamination on exoplanet transmission spectra. MiraSOL uses the Texas Instruments DLP801RE as a spatial light modulator to allow a mask, with 3 arcsecond spatial sampling per micromirror, capable of resolving features on the solar disk. This instrument will have a fiber output which can then be coupled with state-of-the-art extreme precision radial velocity (EPRV) spectrometers, such as HPF or NEID, for high resolving power, stable spectra of sunspots and plage, or a low resolution spectrometer for studies of stellar contamination in transit spectra. We discuss a 60 Hz flicker signal we discovered, likely due to the commercial off-the-shelf (COTS) evaluation board of the digital micromirror device electronics. We also build a proof-of-concept prototype and demonstrate imaging and pixel-level control of the full solar disk to demonstrate the feasibility of this technology.

The CUbesat Solar Polarimeter (CUSP) project aims to measure the linear polarization of solar flares in the 25 - 100 keV hard X-ray band using a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop innovative CubeSat technologies and missions. As part of CUSPs Phase B study, initiated in December 2024 and closed on July 2nd, 2026, estimating the in orbit background to optimize the signal-to-background ratio was one of the key objectives. In low-Earth orbit, the instrument is exposed to cosmic and albedo X-ray backgrounds, charged particles, and secondary radiation from the spacecraft and atmosphere. Simulating these contributions enables optimization of detector geometry and shielding to maximize signal-to-noise performance. We present initial in orbit background estimates for CUSP using a Geant4-based simulator. A detailed mass model of the CUSP has been implemented to simulate background components and estimate the background count rate in the CUSP orbit.

The scientific potential of X-ray polarimetry has long been recognized, yet the challenges of measuring polarization have left it largely unexplored, mainly in the hard X-ray regime. With the advent of hard X-ray focusing optics, sensitive focal-plane Compton polarimeters are now feasible. An early example is CXPOL (Compton X-ray Polarimeter), developed at Physical Research Laboratory (PRL), India, which demonstrated 20 - 80 keV polarimetric capabilities using a plastic scatterer and a CsI(Tl) absorber array. The CXPOL prototype demonstrated polarimetric capabilities in the 20 - 80 keV range, establishing a foundation for further development. Building on this concept, we evaluate a hard X-ray spectro-polarimeter employing a position-sensitive plastic scatterer surrounded by position-sensitive absorber detectors. This geometry enables efficient reconstruction of Compton events and allows combined polarimetric and spectroscopic measurements via interaction positions and deposited energies in the detectors. We evaluate key performance parameters of the revised configuration of the second version of the CXPOL. Using Geant4 simulations, we assess key performance parameters, including modulation factor, polarimetric efficiency, and expected sensitivity with modern hard X-ray optics. We also present the characterization results of first prototype of a 100x20x5 mm3 NaI(Tl) absorber read out on both ends by silicon photomultiplier (SiPM) array operating in coincidence, evaluating energy and position resolution and light-output variation along the detector. The coincidence readout also reduces SiPM background by an order of magnitude. The results demonstrate the strong potential of a position-sensitive Compton- based focal-plane instrument for next-generation hard X-ray spectro-polarimetry.

Core-collapse supernovae are among the most promising yet still undetected sources of gravitational waves. A future detection would provide a direct view of the physical processes occurring deep inside a collapsing star. In this work, we investigate how networks of current and future gravitational-wave detectors can constrain the properties of rapidly rotating core-collapse supernovae using their characteristic core-bounce and early post-bounce signals. Using deep-learning techniques, we estimate the peak frequency, rotation rate, and signal amplitude from noisy detector data and compare the performance of different detector-network configurations. We find that detector networks improve both parameter recovery and sky coverage. For current-generation networks, estimation of the peak frequency is possible out to about 30 kpc, while the rotation rate and signal amplitude remain recoverable out to distances exceeding 100 kpc. Third-generation observatories extend these distances by nearly an order of magnitude.

Pollux is a high-resolution spectropolarimeter proposed by a European consortium for the Habitable Worlds Observatory (HWO). Its design covers a broad spectral range from the far-ultraviolet (FUV) to the near-infrared (97-1 750 nm), with polarimetric channels relying on \ch{MgF2} birefringent optics in the mid- and near-UV (MUV-NUV), and on an innovative all-reflective polarimeter in the FUV, where no birefringent material is available. To validate these polarimeters, whose required polarimetric precision is $10^{-3}$, a dedicated vacuum ultraviolet test bench has been developed, with two configurations: one for the MUV-NUV range (120-290 nm) and one for the FUV range (98-120 nm). We present the first laboratory results obtained with this bench. On the MUV-NUV configuration, the full optical chain has been integrated: a first polarised spectrum of the deuterium lamp was acquired, the polarisation generation subsystem was validated against Mueller matrix predictions, and a first end-to-end polarimetric measurement was performed. On the FUV configuration, the windowless deuterium plasma source has been characterised, the alignment strategy of the K-mirror modulator has been implemented, and the mirror-based analyser has been manufactured and tested, showing a polarisation extinction ratio of 10 at 120 nm. These results demonstrate the operation of the bench and pave the way for the characterisation of the polarimetric precision of the Pollux polarimeters, increasing the Technology Readiness Level of UV spectropolarimetry for HWO.

The Wetterstein Millimeter Telescope (WMT) is a planned broadband (1.2-120 GHz) radio telescope to be established near the Environmental Research Station Schneefernerhaus (UFS) on Germany's highest mountain, the Zugspitze. Developed by a consortium of German research institutes and partners, the WMT is conceived as a multidisciplinary research infrastructure supporting radio astronomy, geodetic VLBI, satellite communications, space situational awareness, and technology development. The telescope is designed to operate within international VLBI networks, including the European VLBI Network, the Global mm-VLBI Array, and future ngVLA and SKA-VLBI observations. This contribution summarizes recent progress in the WMT project, including the evolution of the antenna design, and highlights the potential of the WMT to support future astronomical and geodetic VLBI.

Early detection of major solar flares is critical for defense operations due to their potential to disturb radar and radio systems. Typically, soft X-ray flux is used to monitor and classify solar flares, but since this flux has to be measured in space, it means that its availability itself is dependent on space weather conditions. For this reason, in this paper, we investigated the feasibility of using ground radio observations to monitor major (M5+ class) solar flares. We made use of datasets from the GOES-16 satellite and the Radio Solar Telescope Network in the time range between March 2023 and March 2025. An elastic net regularized logistic regression model was trained on this data, optimized through a grid search and with incorporated class weighting for class imbalance. It was found that especially higher frequencies (8800 MHz) had a reasonable ability in monitoring and predicting major flares (precision and recall for flare events are 53% and 65%, respectively - implying that roughly one third of flares were not detected - with signals appearing, on average, 3 to 4 minutes before the M5 threshold is exceeded). Radio measurements at super high frequencies can thus serve as an alternative method to monitor major solar flaring activity.

The Probe far-Infrared Mission for Astrophysics (PRIMA) will use 8 kilo-pixel kinetic inductance detector (KID) arrays in its spectrometer module. We present an improved resonant frequency to spatial position mapping system designed to preserve each array's mapping after transferring it from the mapping apparatus to the flight housing. Such a mapping is necessary for astronomical observations, and additionally allows us to laser trim the capacitive elements of KIDs to optimize resonance separation in frequency space. This increases the operating yield by eliminating collided resonances, reduces crosstalk, and reduces the sensitivity to frequency drift over time.

Foundation models are high-capacity networks pretrained once on broad data and then reused across many tasks. This chapter introduces them through the idea of a transferable representation, the internal description a network forms during training, which, rather than the fitted task, is what carries over to new problems. We develop the idea from first principles for an astronomical reader, starting from why a representation matters and what makes one useful, and then surveying the architectures, self-supervised objectives, scaling, adaptation, and cross-modal learning that produce one. A theme throughout is the distinction between these methods and the goal they serve. The presence of a transformer, a self-supervised objective, and large-scale pretraining does not by itself make a model a foundation model, since the defining property is that the learned representation transfers, as tested by its ability to work on new tasks with little or no task-specific training data (few-shot and zero-shot learning). We then consider astronomy, where data are abundant but labels are scarce and simulations often stand in for ground truth. Here we offer a cautious reading of the current literature, in which many models adopt the architecture of foundation models while clear demonstrations of transfer across instruments, populations, and tasks remain comparatively rare. This is to be expected, since robust transfer beyond language is still uncommon even in vision and the wider physical sciences, and whether further scaling or a different account of representation will close the gap remains an open question. We close by placing the goal within the broader aim of machine intelligence and outlining the evidence that would mark real progress.

Prime-Cam is a first-generation instrument for the Fred Young Submillimeter Telescope (FYST), enabling wide-field, multi-frequency observations for cosmology, line-intensity mapping, and galaxy studies. We present an optical performance study for a candidate 410 GHz broadband module designed to field approximately 21,000 polarisation-sensitive kinetic inductance detectors (KIDs). The three-lens silicon design was adapted from the SO LATR design and used for the existing 280 and 350 GHz Prime-Cam instrument modules, as well as this study. At 410 GHz, a shorter wavelength places tighter demands on wavefront quality and beam shape. Using Ansys Zemax OpticStudio and Huygens PSF analysis, we evaluate candidate module positions, compare 350 and 410 GHz performance, and assess field-dependent Strehl ratio, ellipticity, and encircled-energy behaviour. A preliminary tolerancing study, using inverse increment and Monte Carlo methods, tests sensitivity to selected alignment perturbations.

Cross-spectral methods have become essential for studying accretion physics in X-ray binaries and active galactic nuclei, where coherence and phase lag measurements constrain physical models and reveal variability components invisible in power spectra alone. Recent multi-Lorentzian fitting techniques have uncovered new quasi-periodic features through joint analysis of power spectra and cross-spectra, but testing these methods requires synthetic data with realistic statistical properties. We present an algorithm for generating pairs of time series with arbitrary power spectra, coherence functions, and phase lag profiles. The method extends existing methods by decomposing the dependent time series into coherent and incoherent components, where the coherent part is constructed through a complex transfer function applied to a reference series. We derive the transfer function and normalization required to preserve target spectral shapes while achieving specified cross-spectral properties. We obtain approximate analytic expressions for the variance of coherence and phase lag estimators and construct the approximate covariance matrix relating these quantities to the underlying power and cross-spectra. When fitting models jointly to power and cross-spectra, these correlations must be incorporated into the likelihood. We apply the method to a two-Lorentzian model with component-specific phase lags and demonstrate close agreement between input models and generated power spectra, coherence function, and phase lag profile across four decades in frequency.

During the 1980s, aerial observations over the Venezuelan Guiana Shield led to the hypothesis that a circular geomorphological feature might represent an impact structure. Radar imagery was subsequently requested and circulated among researchers, but the interpretation remained unresolved. Recently rediscovered correspondence and imagery enabled a re-evaluation using modern digital elevation models from the Shuttle Radar Topography Mission (SRTM). The higher-resolution topographic data indicate that the structure lacks diagnostic morphologies of impact craters and is consistent with the Nuria ring dike intrusive complex. Comparison with analogous circular intrusive complexes, including the Kondyor massif, illustrates how circular morphology alone is insufficient for impact identification. This study documents a historical episode of geomorphological interpretation prior to the availability of modern digital elevation datasets and illustrates how improved topographic information and geological context can clarify the origin of ambiguous circular landforms relevant to planetary surface analysis.

Gravitational waves from compact binary coalescences and from early Universe processes are expected to form a gravitational-wave background. We employ a custom deep learning multi-scale multi-headed autoencoder architecture to isolate gravitational-wave background from detector noise, followed by a Markov chain Monte Carlo inference stage to separate the astrophysical and cosmological components. Analyzing $108$-day mock datasets representative of the first period of the fourth LIGO-Virgo-KAGRA observing run, we show that we can detect with high confidence — $\log_{10}$ noise Bayes factor larger than 3 — a compact binary coalescence gravitational-wave background with an amplitude of $4.3^{+0.5}_{-0.4}\times10^{-9}$ at $f_{\rm ref}=25\,\mathrm{Hz}$, which is a factor $\sim5$ higher than the amplitude expected from compact binary sources. We also show that we can isolate a cosmological – assumed flat spectrum – gravitational-wave background as weak as $ 9.7^{+2.5}_{-2.4} \times 10^{-10}$ from the expected compact binary coalescence gravitational-wave background within simulated Gaussian noise mimicking the LIGO detectors sensitivity achieved in the fourth observing run. In blind-test comparisons with the standard \texttt{pygwb} pipeline, we show that our method achieves more accurate amplitude and spectral-index recovery and enables the separation of astrophysical and cosmological background components.

We present a spectroscopic study of argon electroluminescence (EL) light in a gaseous time projection chamber (TPC). Using a compact detector equipped with photomultiplier tubes with different spectral sensitivities, we measure the light emission in two nominal wavelength regions, approximately [110, 160] nm and [160, 650] nm, at different gas pressures. In addition to the well-known 128 nm emission of the second continuum, significant emission is observed in the [160, 650] nm band, with a prompt, nanosecond-scale response indicating that photon production closely follows the transit of drifting electrons across the high-field EL region. In contrast, the [110, 160] nm emission displays a markedly slower time evolution, dominated by excimer formation and de-excitation dynamics, with the light output governed primarily by the long-lived triplet component of the argon second continuum emission. We demonstrate that the full VUV pulse shape can be reproduced by convolving the fast UV3 response with excimer formation and decay functions, providing a coherent phenomenological interpretation of the observed signals. Our results provide new insights into the spectral and temporal properties of argon electroluminescence and have direct implications for the design and optimization of next-generation rare-event detectors based on gaseous TPCs. Further studies are underway to characterize this emission more precisely and to investigate its potential for particle discrimination.

ler is a Python package for simulating compact-binary gravitational-wave populations and estimating detectable event rates for current and future LIGO-Virgo-KAGRA detector networks. The package provides a unified framework for unlensed and strongly lensed binary black hole, binary neutron star, and neutron star-black hole mergers. It samples source and lens populations, evaluates detector selection effects, solves lens equations for strongly lensed systems, and computes image properties such as magnifications and time delays. The framework supports multiple source-population and lens models, including SIS, SIE, and EPL plus external shear, and allows users to replace default distributions and detection criteria through modular interfaces. Computational efficiency is obtained through vectorized sampling, inverse-transform and importance-sampling strategies, multiprocessing, and just-in-time compiled routines. ler is designed for large-scale Monte Carlo studies in which rates and selected populations must be evaluated repeatedly, including forecasts for observing runs, studies of lensing candidate validation, and selection-function calculations for population inference. The package is distributed with documentation, validation examples, and reproducible workflows.

Gravitational waves from core-collapse supernovae are a promising yet challenging target for detection due to the stochastic and complex nature of these signals. Conventional detection methods for core-collapse supernovae rely on excess energy searches because matched filtering has been hindered by the lack of well-defined waveform templates. However, numerical simulations of core-collapse supernovae have improved our understanding of the gravitational wave signals they emit, which enables us, for the first time, to construct a set of templates that closely resemble predictions from numerical simulations. In this study, we investigate the possibility of detecting gravitational waves from core-collapse supernovae using template-based methods. We construct a theoretically-informed template bank and use it to recover core-collapse supernova signals injected into real LIGO-Virgo-KAGRA detector data. We consider the signals from three state-of-the-art numerical models, simulated with three different codes. We evaluate the detection efficiency of the template-filtering approach and how well the injected signal is reconstructed. For signals whose structure is well captured by our template bank, we recover  90% of injections at a distance of 1 kpc and  30-60% at 2 kpc. In contrast, a model whose signal differs significantly from the templates is recovered less efficiently. For many of the recovered events, the underlying signal characteristics can be reconstructed with an accuracy of  10-20%. We discuss the strengths and limitations of this approach and identify areas for further improvements for template-based methods for supernova gravitational-wave detection. We also present the open-source Python package SynthGrav used to generate the template bank.

Low-temperature systems play a vital role in a variety of scientific research applications, including the next generation of cosmology and astrophysics telescopes. More ambitious cryogenic applications require precise estimates of the thermal conductivity of materials and thermal joints to meet project goals. We present the development of the Cryogenic Material Repository (CMR), a public GitHub repository of cryogenic material properties data created to support and enable researchers across scientific disciplines to accurately and efficiently design and assess cryogenic systems. We also present updated sub-Kelvin thermal conductivity results for select carbon fiber reinforced polymer and aluminum alloy samples.

In gravitational-wave astronomy, as in other scientific disciplines, “exceptional” sources attract considerable interest because they challenge our current understanding of the underlying (astro)physical processes. Crucially, “exceptionality” is defined only relative to the rest of the detected population. For instance, among all gravitational-wave events detected so far, GW231123 is the binary black hole with the largest total mass, while GW241110 is the binary black hole with the most strongly misaligned spin relative to the orbital angular momentum. Mandel [Astrophys. J. Lett. 996, L4 (2026)] argued that apparent “exceptionality” may reflect measurement error rather than an extreme true value, and suggested that the total mass of GW231123 may be significantly overestimated. Here we present a quantitative analysis that supports this conceptual point. We find that claims of “exceptionality” obtained under population-agnostic priors should be critically questioned whenever measurement uncertainties are comparable to the width of the underlying population. Specifically, we find that the total mass of GW231123 is unlikely to be meaningfully affected by this effect while the spin of GW241110 is far less likely to be antialigned than initially claimed: about 70% of realizations that appear to yield an “exceptionally antialigned” spin are in fact consistent with either nonspinning or aligned configurations.

Traditional weak gravitational lensing shear estimators are carefully calibrated but struggle to fully capture realistic galaxy morphologies, point-spread-function (PSF) effects, blending, and noise in deep surveys, while blindly trained machine learning (ML) models can introduce significant calibration biases. Here we construct a fully D$_4$-equivariant deep neural network for galaxy shape measurement whose architecture enforces symmetry under 90$^{\circ}$ rotations and mirror transformations, and adopt the Analytical Calibration framework (AnaCal) to calibrate the model using its backpropagated gradients. For isolated galaxies in LSST-like single-band simulations, we demonstrate that our approach achieves $\sim$10% lower shape noise than the traditional moment-based Fourier Power Function Shapelets estimator in the high-noise regime, equivalent to a $\sim$20% gain in effective galaxy number density, while simultaneously achieving multiplicative biases consistent with zero across a wide range of noise levels, PSF sizes and ellipticities, and magnitude selection cuts, with all measurements satisfying $|m| {<} 2 \times 10^{-3}$ (i.e., within the 0.2% LSST requirement) and most at the ${\sim}10^{-4}$ level. We demonstrate this framework on isolated single-band galaxy images with Gaussian noise and known PSF, establishing a rigorous, physics-informed foundation for future extensions of ML-based shear estimation to blended sources and multi-band observations in Stage-IV surveys. All codes and data products will be made publicly available upon acceptance.

Solar radio bursts are important signatures of dynamic processes in the solar corona, including particle acceleration and shock propagation associated with solar flares and coronal mass ejections. Among the missions that report solar radio bursts within 24 hours, the e-CALLISTO archive is the largest, with more than 150 stations worldwide. The archive generates large volumes of FITS data that are often affected by radio-frequency interference and background noise. Irregular frequency setups in different stations are also a limitation of statistical analysis of SRBs. Each CALLISTO observation is a 15-minute frame, which often causes a single burst to split over multiple frames, making event-level analysis difficult. This work presents the e-CALLISTO FITS Analyzer, a unified, interactive, cross-platform application for processing and analyzing e-CALLISTO dynamic spectra on Windows, macOS, and Linux. The application supports time and frequency merging to produce a continuous spectrum, applies mean background subtraction with user-controlled threshold clipping, and isolates burst regions through an interactive polygon mask in the time-frequency plane. It also extracts the maximum-intensity backbone, allows interactive outlier removal, and performs power-law fitting to estimate drift rates and derive shock height and speed using the Newkirk model, including $n$-fold scaling. For a Type II burst observed by Arecibo Observatory on 2 March 2022, the analyzer yielded an average drift rate of $-0.0400 \pm 0.0003\, MHz/s$ and an average shock speed of $449 \pm 1\, km/s$ at a height of $1.715 \pm 0.002\, R_{\odot}$. The e-CALLISTO FITS Analyzer supports more reproducible, event-focused SRB analysis and improves access to physically meaningful measurements from e-CALLISTO FITS data.

We present DEtection in phase-folded Light curves with cOntrastive Scoring (DELOS), a contrastive-learning-based framework designed to search for shallow transits in Kepler photometry. DELOS combines GPU-accelerated phase folding, optimized phase binning, and a custom one-dimensional convolutional encoder to assign a transit-likeness score to each folded light curve, thereby producing a score periodogram over trial periods without relying on pre-detected threshold-crossing events. Focusing on intermediate-to-long-period signals with orbital periods of 100-150 days, DELOS was trained on 20 million synthetic light curves generated with realistic transit models and Kepler-like noise properties, achieving a validation accuracy of 99.3 percent on the synthetic validation set. In controlled injection-recovery experiments, DELOS improves the combined precision-recall performance by 15.5 percent relative to Box-fitting Least Squares (BLS) and 11.25 percent relative to Transit Least Squares (TLS) in the low Signal-to-Noise Ratios (low-SNR) regime. It also accelerates the search by factors of approximately 3-5 and 74-80 compared with BLS and TLS, respectively. Applied to a selected Kepler validation sample, DELOS recovered all known shallow intermediate-to-long-period transit signals in the tested period range. These results demonstrate that DELOS provides an efficient and sensitive framework for low-SNR transit searches and represents a practical step toward future searches for longer-period terrestrial planets in Kepler, K2, TESS, PLATO, and Earth 2.0 data. Accordingly, this work is intended as a methodological development and validation study, with the detailed astrophysical validation of newly identified candidates deferred to future work.

The Transiting Exoplanet Survey Satellite (TESS) has transformed the study of nearby exoplanetary systems; however, its nominal observing strategy limits sensitivity to planets with orbital periods shorter than $\sim$10 days for most parts of the sky. The two TESS Continuous Viewing Zones (CVZs) provide extended temporal baselines that help overcome this limitation, enabling the detection of longer-period ($>$10 days) transiting planets around nearby stars. Here, we present COUNTESS, a transit-search pipeline optimized for long-baseline TESS observations that combines multi-sector light curves with heterogeneous cadences, and implements fast-folding BLS period detection, vetting, and statistical validation. As a first application of the pipeline, we conducted a search on the primary and first extended mission photometry in the TESS northern CVZ. For this analysis, we used Gaia DR3 and 2MASS photometry to homogeneously derive a stellar catalog of FGKM stars for the TESS northern CVZ, resulting in a sample of 391,059 stars. We used COUNTESS to search for transiting planets around 26,114 of these stars with TESS-SPOC light curves and assessed its performance, recovering 115 out of 159 known TESS Objects of Interest (TOIs; $0.85\ \text{days} < P <124.72\ \text{days}$; $1.03\ R_\oplus < R_p < 16.35\ R_\oplus$). Additionally, we identified 10 new exoplanet candidates ($1.20\ \text{days} < P <34.62\ \text{days}$; $1.73\ R_\oplus < R_p < 4.19\ R_\oplus$) that passed vetting tests, including two new statistically validated sub-Neptunes, TIC 219893931b and TIC 237254473b. COUNTESS enables extended-baseline TESS analyses and identification of longer-period planets, establishing a foundation for future exoplanet demographic studies, including comparisons with Kepler and K2.

We present the Stream Graph Navigator (SGN), a lightweight Python framework for building streaming data applications. In SGN, stream-processing pipelines are built by connecting computational components into directed acyclic graphs that run within an event loop. The time-series extension of the SGN library, SGN-TS, introduces signal processing methods to handle time series data. Together, SGN and SGN-TS provide the foundation for SGNL, a matched-filtering gravitational-wave search pipeline, and are being adopted by multiple projects across the low-latency gravitational-wave data analysis infrastructure as an extensible and maintainable framework for future gravitational-wave observations.

We present a reproducible method for predicting atmospheric re-entries using only publicly available Two-Line Elements (TLEs). The approach is based on a segmented calibration of the effective mass-to-area ratio (M/A), adjusted independently over intervals of at least 12 hours to suppress short-period catalogue noise. Longer segments provide a stable dynamical signal from which the effective drag behaviour can be retrieved. Applied to recent natural re-entries of rocket bodies, debris, and non-manoeuvring satellites, the method consistently identifies the final orbital revolution and reproduces published Tracking and Impact Prediction (TIP) times with an accuracy of approximately +/- 1 hour in the terminal phase. The limiting factor is the intrinsic noise and cadence of the TLE catalogue rather than atmospheric or solar-flux modelling. Within these constraints, segmented M/A calibration offers a transparent, lightweight, and operationally robust alternative for re-entry analysis when only public data are available.

Blending will be a major source of systematic uncertainty in downstream science analyses of LSST data. We benchmark the performance of several deblenders, leveraging the Blending ToolKit (BTK) to perform rigorous, end-to-end testing. This benchmark incorporates key deblending algorithms, including SourceExtractor, SCARLET, and DeepDISC, with the goal of comparing their effectiveness in handling blended galaxy images from LSST/Rubin simulations. A key focus is characterizing algorithm performance in the regime of unrecognized blends, where multiple galaxies are misidentified as a single object, as these cases introduce systematic biases that propagate into downstream cosmological analyses for galaxy surveys. By utilizing BTK's ability to create customized, reproducible blends, we systematically test these deblenders against different blending conditions, such as source separation and brightness. The toolkit's standardized evaluation metrics, including detection precision, segmentation accuracy, and source reconstruction, are comprehensive assessments of each algorithm's strengths and limitations. Each deblender has performance caveats that may impact their true performance in real survey conditions. We find that SCARLET has high segmentation and reconstruction performance, whereas DeepDISC has strong detection recall for faint and low-SNR sources, and SourceExtractor has accurate peak finding abilities but low segmentation and reconstruction performance. This benchmark provides valuable insights into the performance of existing deblenders and highlights areas for future development.