Saint Mary’s University
We report an updated mass and magnification model of galaxy cluster Abell 370 using new NIRCam and NIRISS data from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using Lenstool and a combination of archival HST and MUSE data with new JWST data as constraints, we derive an improved gravitational lensing model and extract magnifications of background galaxies with uncertainties. Using our best fit model, we perform a search for new multiply imaged systems via predicted positions. We report no new multiply imaged systems with identifiable redshifts, likely due to already very deep HST and Spitzer data, but confirm a z8z\sim8 multiply imaged system by measuring its redshift with NIRISS and NIRSpec spectra. We find that the overall shape of the critical curve for a source at z=9.0z = 9.0 is similar to previous models of Abell 370, with small changes. We investigate the z8z\sim8 galaxy with two images observable with an apparent magnitude in the F125W band of 26.0±0.226.0\pm0.2 and 25.6±0.125.6\pm0.1. After correcting for the magnifications of the images, 7.21.2+0.2^{+0.2}_{-1.2} and 8.70.4+0.4^{+0.4}_{-0.4}, we use SED fitting to find an intrinsic stellar mass of log(M/M)M^*/M_{\odot}) = 7.350.05+0.04^{+0.04}_{-0.05}, intrinsic SFR of 3.51.4+2.2^{+2.2}_{-1.4} M_{\odot}/yr, and MUVM_{UV} of -21.30.2+0.2^{+0.2}_{-0.2}, which is close to the knee of the luminosity function at that redshift. Our model, and corresponding magnification, shear, and convergence maps are available on request and will be made publicly available on MAST in a CANUCS data release (DOI: 10.17909/ph4n-6n76).
Researchers at Saint Mary ’s University introduced Point-JEPA, a self-supervised learning framework that adapts the Joint-Embedding Predictive Architecture to 3D point clouds using a novel greedy sequencer for spatial ordering. The model achieves state-of-the-art classification accuracy of 93.7% on ModelNet40 with significantly reduced pre-training time (7.5 hours).
While the James Webb Space Telescope (JWST) now allows identifying quiescent galaxies (QGs) out to early epochs, the photometric selection of quiescent galaxy candidates (QGCs) and the derivation of key physical quantities are highly sensitive to the assumed star-formation histories (SFHs). We aim to quantify how the inclusion of JWST/MIRI data and different SFH models impacts the selection and characterisation of QGCs. We test the robustness of the physical properties inferred from the spectral energy distribution (SED) fitting, such as M*, age, star formation rate (SFR), and AV, and study how they impact the quiescence criteria of the galaxies across cosmic time. We perform SED fitting for ~13000 galaxies at z<6 from the CEERS/MIRI fields with up to 20 optical-mid infrared (MIR) broadband coverage. We implement three SFH prescriptions: flexible delayed, NonParametric, and extended Regulator. For each model, we compare results obtained with and without MIRI photometry and dust emission models. We evaluate the impact of these configurations on the number of candidate QGCs, selected based on rest UVJ colours, sSFR and main-sequence offset, and on their key physical properties such as M*, AV, and stellar ages. The number of QGCs selected varies significantly with the choice of SFH from 171 to 224 out of 13000 galaxies, depending on the model. This number increases to 222-327 when MIRI data are used (up to ~45% more QGCs). This enhancement is driven by improved constraints on dust attenuation and M*. We find a strong correlation between AV and M*, with massive galaxies (M*~10^11 M\odot) being 1.5-4.2 times more attenuated in magnitude than low-mass systems (M*~10^9 M\odot), depending on SFH. Regardless of the SFH assumption, ~13% of QGCs exhibit significant attenuation (AV > 0.5) in support of recent JWST studies challenging the notion that quiescent galaxies are uniformly dust-free.
We present measurements of stellar population properties of a newly discovered spectroscopically confirmed z=11.100.26+0.11z=11.10^{+0.11}_{-0.26}, gravitationally lensed galaxy, using JWST NIRSpec PRISM spectroscopy and NIRCam imaging. The arc is highly magnified by the Bullet Cluster (magnification factor μ=14.00.3+6.2{\mu}=14.0^{+6.2}_{-0.3}. It contains three star-forming components of which one is barely resolved and two are unresolved, giving intrinsic sizes of 10pc\lesssim 10pc. The clumps also contain ~50% of the total stellar mass. The galaxy formed the majority of its stars ~150Myr ago (by z~14). The spectrum shows a pronounced damping wing, typical for galaxies deep in the reionisation era and indicating a neutral IGM at this line of sight. The intrinsic luminosity of the galaxy is 0.0860.030+0.008L0.086^{+0.008}_{-0.030} L^* (with LL^* being the characteristic luminosity for this redshift), making it the lowest luminosity spectroscopically confirmed galaxy at z>10z>10 discovered to date.
This paper explores the advancements and applications of language models in healthcare, focusing on their clinical use cases. It examines the evolution from early encoder-based systems requiring extensive fine-tuning to state-of-the-art large language and multimodal models capable of integrating text and visual data through in-context learning. The analysis emphasizes locally deployable models, which enhance data privacy and operational autonomy, and their applications in tasks such as text generation, classification, information extraction, and conversational systems. The paper also highlights a structured organization of tasks and a tiered ethical approach, providing a valuable resource for researchers and practitioners, while discussing key challenges related to ethics, evaluation, and implementation.
The Cosmic Evolution Survey (COSMOS) has become a cornerstone of extragalactic astronomy. Since the last public catalog in 2015, a wealth of new imaging and spectroscopic data has been collected in the COSMOS field. This paper describes the collection, processing, and analysis of this new imaging data to produce a new reference photometric redshift catalog. Source detection and multi-wavelength photometry is performed for 1.7 million sources across the 2deg22\,\mathrm{deg}^{2} of the COSMOS field, \sim966,000 of which are measured with all available broad-band data using both traditional aperture photometric methods and a new profile-fitting photometric extraction tool, The Farmer, which we have developed. A detailed comparison of the two resulting photometric catalogs is presented. Photometric redshifts are computed for all sources in each catalog utilizing two independent photometric redshift codes. Finally, a comparison is made between the performance of the photometric methodologies and of the redshift codes to demonstrate an exceptional degree of self-consistency in the resulting photometric redshifts. The i&lt;21 sources have sub-percent photometric redshift accuracy and even the faintest sources at $25
We present an overview of the MINERVA survey, a 259.8 hour (prime) and 127 hour (parallel) Cycle 4 treasury program on the James Webb Space Telescope (JWST). MINERVA is obtaining 8 filter NIRCam medium band imaging (F140M, F162M, F182M, F210M, F250M, F300M, F360M, F460M) and 2 filter MIRI imaging (F1280W, F1500W) in four of the five CANDELS Extragalactic fields: UDS, COSMOS, AEGIS and GOODS-N. These fields were previously observed in Cycle 1 with 7 - 9 NIRCam filters by the PRIMER, CEERS and JADES programs. MINERVA reaches a 5σ\sigma depth of 28.1 mag in F300M and covers \sim 542 arcmin2^2, increasing the area of existing JWST medium-band coverage in at least 8 bands by \sim 7×\times. The MIRI imaging reaches a 5σ\sigma depth of 23.9 mag in F1280W and covers \sim 275 arcmin2^2 in at least 2 MIRI filters. When combined with existing imaging, these data will provide a photometric catalog with 20-26 JWST filters (depending on field) and 26-35 filters total, including HST. This paper presents a detailed breakdown of the filter coverage, exposure times, and field layout relative to previous observations, as well as an overview of the primary science goals of the project. These include uncovering the physics of enigmatic sources hiding in current broadband catalogs, improving systematics on stellar mass functions and number densities by factors of \gtrsim 3, and resolved mapping of stellar mass and star formation at 1 &lt; z &lt; 6. When complete, MINERVA will become an integral part of the treasury deep field imaging datasets, significantly improving population studies with well-understood completeness, robust photometric redshifts, stellar masses, and sizes, and facilitating spectroscopic follow up for decades to come.
The Little Red Dot (LRD) paradigm comprises three main unknowns that are intrinsically connected: (1) What is the nature of these sources? (2) How do they form? (3) How do they evolve? Larger spectroscopic samples and high-resolution data are needed to delve deeper into the mechanisms ruling these sources. Understanding their formation and evolution requires identifying the rise and fall of the key features that characterize these systems, such as their compactness and ``V''-shaped spectral energy distributions. In this work, we present a galaxy system nicknamed The Stingray that was identified in the Canadian NIRISS Unbiased Cluster Survey (CANUCS). This group contains three sources at zspec=5.12z_{\mathrm{spec}} = 5.12, including an active galactic nucleus (AGN), a Balmer break galaxy, and a star-forming satellite. The latter resembles a Building Block System in which interactions boost stellar mass and black hole mass growth beyond what is expected from secular processes alone. The AGN in this system exhibits features indicative of a transitional object, bridging a normal AGN and an LRD phase. These are a blue rest-frame ultraviolet slope, compact size, and a broad Hα\alpha line (all of which are characteristic of LRDs), but a flatter rest-frame optical slope compared to that observed in LRDs. The features in this source point to the emergence or fading of an LRD, potentially triggered by environmental effects.
We have determined stellar mass functions of 120 Milky Way globular clusters and massive LMC/SMC star clusters based on a comparison of archival Hubble Space Telescope photometry with a large grid of direct N-body simulations. We find a strong correlation of the global mass function slopes of star clusters with both their internal relaxation times as well as their lifetimes. Once dynamical effects are being accounted for, the mass functions of most star clusters are compatible with an initial mass function described by a broken power-law distribution N(m)mαN(m) \sim m^\alpha with break masses at 0.4 M_\odot and 1.0 M_\odot and mass function slopes of αLow=0.3\alpha_{Low}=-0.3 for stars with masses m&lt;0.4 M_\odot, αHigh=2.30\alpha_{High}=-2.30 for stars with m&gt;1.0 M_\odot and αMed=1.65\alpha_{Med}=-1.65 for intermediate-mass stars. Alternatively, a log-normal mass function with a characteristic mass logMC=0.36\log M_C = -0.36 and width σC=0.28\sigma_C=0.28 for low-mass stars and a power-law mass function for stars with m&gt;1 M_\odot also fits our data. We do not find a significant environmental dependency of the initial mass function with either cluster mass, density, global velocity dispersion or metallicity. Our results lead to a larger fraction of high-mass stars in globular clusters compared to canonical Kroupa/Chabrier mass functions, increasing the efficiency of self-enrichment in clusters and helping to alleviate the mass budget problem of multiple stellar populations in globular clusters. By comparing our results with direct N-body simulations we finally find that only simulations in which most black holes are ejected by natal birth kicks correctly reproduce the observed correlations.
One of the most surprising results of early James Webb Space Telescope (JWST) observations is the discovery of an abundance of red, compact, broad-line objects dubbed "little red dots" (LRDs) at z&gt;4. Their spatial density (104\sim10^{-4}-105cMpc310^{-5}\,\mathrm{cMpc^{-3}}) is 100 times more abundant than UV-selected quasars at those redshift if one extrapolates the quasar luminosity function (QLF) down to the LRD regime. However, whether LRDs dominate black hole accretion at quasar-like luminosities (Lbol104546ergs1L_\mathrm{bol}\gtrsim 10^{45-46}\,\mathrm{erg\,s^{-1}}) remains unanswered, as probing the bright end of the LRD luminosity function requires a much larger area than those able to be surveyed by JWST. In this work, we present our search for the brightest LRDs (K&lt;23.7) at $4.5
We present the first data release of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), a JWST Cycle 1 GTO program targeting 5 lensing clusters and flanking fields in parallel (Abell 370, MACS0416, MACS0417, MACS1149, MACS1423; survey area \tilda100 arcmin2^{2}), with NIRCam imaging, NIRISS slitless spectroscopy, and NIRSpec prism multi-object spectroscopy. Fields centered on cluster cores include imaging in 8 bands from 0.9-4.4μ\mum, alongside continuous NIRISS coverage from 1.15-2μ\mum, while the NIRCam flanking fields provide 5 wide and 9 medium band filters for exceptional spectral sampling, all to \tilda29 magAB_{AB}. We also present JWST in Technicolor, a Cycle 2 follow-up GO program targeting 3 CANUCS clusters (Abell 370, MACS0416, MACS1149). The Technicolor program adds NIRISS slitless spectroscopy in F090W to the cluster fields while adding 8 wide, medium, and narrow band filters to the flanking fields. This provides NIRCam imaging in all wide and medium band filters over \tilda30 arcmin2^{2}. This paper describes our data reduction and photometry methodology. We release NIRCam, NIRISS, and HST imaging, PSFs, PSF-matched imaging, photometric catalogs, and photometric and spectroscopic redshifts. We provide lens models and stellar population parameters in up to 19 filters for \tilda53,000 galaxies in the cluster fields, and \tilda44,000 galaxies in up to 29 filters in the flanking fields. We further present 733 NIRSpec spectra and redshift measurements up to z=10.8z=10.8. Comparing against our photometric redshifts, we find catastrophic outlier rates of only 4-7\% and scatter of σNMAD\sigma_{\rm NMAD} of 0.01-0.03.
JWST has revealed unexpectedly bright galaxies in the first 500 Myr after the Big Bang. Their overabundance suggests that they are preferentially observed during burst phases, where their star formation rates increase dramatically. In cosmological simulations, such bursts transition into short (40\approx 40 Myr) periods without star formation or naps. Using JWST/NIRCam medium-band observations, we report the discovery of the galaxy CANUCS-A370-2228423 (z=5.95±0.06z = 5.95 \pm 0.06, log(M/M)=9.14±0.09\log(M_\ast/M_{\odot}) = 9.14 \pm 0.09), dubbed The Sleeper. Its star formation history indicates rapid assembly in the first 300 Myr (z14z \gtrsim 14), where it formed a log(M/M)=8.70.4+0.3 M\log(M_\ast/M_{\odot}) = 8.7^{+0.3}_{-0.4}\ M_{\odot} progenitor, comparable in stellar mass to the few spectroscopically confirmed galaxies at those redshifts. Unexpectedly, this is followed by several hundred million years of suppressed star formation, in stark contrast to nappers. This results in a remarkably strong hydrogen Balmer break, exceeding that of any galaxy observed within the first billion years by a factor of 3\approx 3. Furthermore, Sleeper-like systems are overabundant in the observed survey volume compared to theory, as the probability of finding such galaxies in simulations is &lt; 0.2\%. The discovery of The Sleeper therefore disrupts the current narrative that all luminous galaxies in the first few hundred million years grow into massive descendants. Instead it presents an alternative evolutionary pathway in which these unusually luminous galaxies fade into inefficient dwarfs after an early starburst, revealing greater diversity in the first stages of galaxy evolution.
Encoded within the morphological structure of galaxies are clues related to their formation and evolutionary history. Recent advances pertaining to the statistics of galaxy morphology include sophisticated measures of concentration (C), asymmetry (A), and clumpiness (S). In this study, these three parameters (CAS) have been applied to a suite of simulated galaxies and compared with observational results inferred from a sample of nearby galaxies. The simulations span a range of late-type systems, with masses between ~1e10 Msun and ~1e12 Msun, and employ star formation density thresholds between 0.1 cm^-3 and 100 cm^-3. We have found that the simulated galaxies possess comparable concentrations to their real counterparts. However, the results of the CAS analysis revealed that the simulated galaxies are generally more asymmetric, and that the range of clumpiness values extends beyond the range of those observed. Strong correlations were obtained between the three CAS parameters and colour (B-V), consistent with observed galaxies. Furthermore, the simulated galaxies possess strong links between their CAS parameters and Hubble type, mostly in-line with their real counterparts.
We present an initial analysis of the X-Ray Imaging and Spectroscopy Mission (XRISM) first-light observation of the supernova remnant (SNR) N132D in the Large Magellanic Cloud. The Resolve microcalorimeter has obtained the first high-resolution spectrum in the 1.6-10 keV band, which contains K-shell emission lines of Si, S, Ar, Ca, and Fe. We find that the Si and S lines are relatively narrow, with a broadening represented by a Gaussian-like velocity dispersion of σv450\sigma_v \sim 450 km s1^{-1}. The Fe Heα\alpha lines are, on the other hand, substantially broadened with σv1670\sigma_v \sim 1670 km s1^{-1}. This broadening can be explained by a combination of the thermal Doppler effect due to the high ion temperature and the kinematic Doppler effect due to the SNR expansion. Assuming that the Fe Heα\alpha emission originates predominantly from the supernova ejecta, we estimate the reverse shock velocity at the time when the bulk of the Fe ejecta were shock heated to be $-1000 \lesssim V_{\rm rs}~[{\rm km s}^{-1}] \lesssim 3300$ (in the observer frame). We also find that Fe Lyα\alpha emission is redshifted with a bulk velocity of 890\sim 890 km s1^{-1}, substantially larger than the radial velocity of the local interstellar medium surrounding N132D. These results demonstrate that high-resolution X-ray spectroscopy is capable of providing constraints on the evolutionary stage, geometry, and velocity distribution of SNRs.
Stellar-mass black holes are the final remnants of stars born with more than 15 solar masses. Billions are expected to reside in the Local Group, yet only few are known, mostly detected through X-rays emitted as they accrete material from a companion star. Here, we report on VFTS 243: a massive X-ray faint binary in the Large Magellanic Cloud. With an orbital period of 10.4-d, it comprises an O-type star of 25 solar masses and an unseen companion of at least nine solar masses. Our spectral analysis excludes a non-degenerate companion at a 5-sigma confidence level. The minimum companion mass implies that it is a black hole. No other X-ray quiet black hole is unambiguously known outside our Galaxy. The (near-)circular orbit and kinematics of VFTS 243 imply that the collapse of the progenitor into a black hole was associated with little or no ejected material or black-hole kick. Identifying such unique binaries substantially impacts the predicted rates of gravitational-wave detections and properties of core-collapse supernovae across the Cosmos.
Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes.
Recent discoveries of dust and molecular gas in quiescent galaxies (QGs) up to z3z\sim3 challenge the long-standing view that the interstellar medium depletes rapidly once star formation ceases, raising key questions of whether dust and gas co-evolve in QGs, and how their depletion links to stellar aging. We present deep Atacama Large Millimeter/submillimeter Array (ALMA) Band~6 continuum and CO(3--2) observations of 17 QGs at z0.4z\sim0.4 in the COSMOS field. Using the dust-to-molecular gas mass ratio (δDGR\delta_{\rm DGR}) as a key diagnostic, we trace post-quenching evolution of the cold interstellar medium. Our study triples the number of QGs with direct δDGR\delta_{\rm DGR} estimates, constraining 12 systems with stellar population ages of \sim5--10 Gyr. For the first time, we show that δDGR\delta_{\rm DGR} in QGs ranges from 8×\sim8\times below to 2.5×\sim2.5\times above the canonical value of δDGR1/100\delta_{\rm DGR}\sim1/100. Despite uniformly low molecular gas fractions (median fH2=MH2/M4.1%f_{\rm H_2}=M_{\rm H_2}/M_{\star}\sim4.1\%), QGs follow diverse evolutionary paths: about half exhibit rapid (700\sim700 Myr) exponential dust decline with age, while the rest show mild decline over \gtrsim2 Gyr, maintaining elevated δDGR1/100\delta_{\rm DGR}\gtrsim1/100. Our results support simulations predictions of dust and molecular gas evolving independently post-quenching, without a preferred quenching mode. This challenges the use of dust continuum as a H2\rm H_2 tracer, implying that quenching cannot be robustly linked to interstellar medium conditions when relying solely on dust or gas.
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