arXiv subjects

Michael D. Gladders

Publications and source records attributed to Michael D. Gladders.

At least 19 recordsLinked to original sources

arXiv2026

LEGGOS: A Shocking Lack of Evidence for Shocks at sub-kiloparsec Scales at 2 < z < 4

Here we present the first systematic search for shocks in six gravitationally lensed galaxies at 2.37 < z < 3.625 with JWST/NIRSpec integral field spectroscopy from the LEnsing and Galaxy Growth: Observing Substructures (LEGGOS) survey. We employ diagnostics that utilize the fluxes and kinematics of shock-sensitive rest-frame optical emission lines H\b{eta}, [O iii] λ5008, [O i] λ6302, Hα, [N ii] λ6585, and [S ii] λλ6718, 6733. We find that, on pixel, clump, and galaxy-integrated scales, the LEGGOS spectra show minimal if any evidence for shocks. The image plane pixels are < 8% within the shock regions of the rest-frame optical line ratio diagnostics for any individual galaxy, and the shock-identified pixels do not show a coherent spatial structure. We also leverage MAPPINGS V shock models to infer shock velocities from the observed emission lines, and find that the distributions of inferred shock velocities are inconsistent with those expected for shock-dominated gas. Altogether, none of these methods provide significant evidence for shocks in the six LEGGOS sources. We conclude by discussing the implications of the lack of evidence for shocks in the broader context of galaxy evolution at cosmic noon and earlier epochs.

astro-ph.GA↗

arXiv2026

LEGGOS: Direct abundances of N, O, Ne, S, and Ar in five lensed galaxies at Cosmic Noon

We present direct $T_e$ chemical abundances in five strongly lensed galaxies at Cosmic Noon ($2.481 \leq z \leq 3.625$) using JWST/NIRSpec data from the LEGGOS survey. We measure gas-phase abundances of N, O, S, and Ar in all five galaxies, and Ne in two galaxies. Three galaxies have electron temperature constraints from multiple different ionization zones, and we find that these are broadly consistent with temperature scaling relations observed in both local and high-$z$ galaxies. We find a range of oxygen abundances $8.04 \leq 12+\log(\text{O/H}) \leq 8.79$ (22 -- 126\% $Z_{\odot}$). The ratios of N/O and Ne/O are consistent with trends observed in local galaxies. We do not observe any evidence for significant N enhancement in our sample, though the youngest galaxy in our sample (SGAS-J1050) has a mildly elevated $\log(\text{N/O}) = 1.20 \pm 0.08$, which we suggest may be driven by a population of young massive stars. The ratios of S/O and Ar/O are generally sub-solar, similar to trends observed in other high-$z$ galaxies. We find that the S/O and Ar/O abundances are sub-solar, consistent with enrichment from core-collapse supernovae (CCSNe). Modeling of the star formation histories of the LEGGOS galaxies supports CCSNe enrichment, as each galaxy shows a recent period of star formation lasting $\lesssim 100$ Myr, indicating that type Ia supernovae would not yet have had enough time to contribute significantly to the gas-phase abundances of these galaxies.

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arXiv2026

LEGGOS I: The JWST LEGGOS Survey -- LEnsing and Galaxy Growth: Observing Substructures -- Unpacks the Nature of Clumpy Star Formation and Quenching in Gravitationally Lensed Galaxies beyond Cosmic Noon

We present first results from the JWST LEGGOS Survey (LEnsing and Galaxy Growth: Observing Substructures), aimed at studying the physics of clumpy star formation and quenching in eight lensed galaxies at $z\sim2$--4. LEGGOS combines multiple Cycle 2 JWST GO programs (GO 4125, GO 3843) and Cycle 1 archival data, and utilizes strong gravitational lensing with NIRCam imaging and NIRSpec integral-field spectroscopy. LEGGOS targets UV-bright, highly magnified systems to resolve $\sim$10--200 pc regions in both rest-frame optical continuum and nebular emission. This overview paper describes the survey design, data reduction and calibration strategy, and science-quality data products, and highlights early examples demonstrating how spectroscopy breaks key degeneracies inherent to photometry-only clump studies, including identifying recent quenching in previously-thought UV star forming galaxies. We introduce a uniform analysis framework that jointly models lensing reconstruction, multi-band photometry, and integral field spectroscopy to disentangle multiple stellar populations within individual clumps and their surrounding diffuse regions. Using maps of Balmer recombination lines and key emission line diagnostic ratios, we connect star formation histories, dust attenuation, and nebular conditions on sub-kpc scales -- LEGGOS galaxies range from uniform metallicities across the whole galaxy, to having higher clump metallicities and harder ionization conditions relative to diffuse regions. The full survey dataset, with simultaneous flux and morphology constraints on clumpy source-plane regions, and a flexible spectrophotometric SPS modeling approach, provides a direct bridge between parsec-scale star formation physics and galaxy assembly at and beyond cosmic noon, offering a robust and efficient means of resolving star formation in the first galaxies.

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arXiv2026

LEGGOS II: A Strong Lens Model and Source-Plane Projection of the Clumpy Star-Forming Galaxy SGASJ111020.0+645950.8 at z=2.48

Strong gravitational lensing by galaxy clusters combined with the resolution of JWST enables studies of star formation on ~10-100 pc scales in galaxies at z~2-4. As part of the LEnsing and Galaxy Growth: Observing Substructures survey (LEGGOS), we present an updated strong lensing model of the galaxy cluster SDSSJ1110+6459 (z=0.659), which lenses the clumpy star-forming galaxy SGASJ111020.0+645950.8 at z=2.481 into a highly magnified giant arc. Using JWST NIRCam imaging, NIRSpec spectroscopy, and archival HST data, we confirm and refine the identification of four multiply imaged background sources, including one newly identified system, and map over 20 luminous regions between each image of the primary arc. Spectroscopy confirms that several previously ambiguous edge "clumps" belong to the main arc at z=2.481. Despite the limited number of strongly lensed sources in the field, the resulting lens model has high precision, owing to the high density of JWST-resolved clump constraints that tightly probe the lensing potential near the giant arc. The model yields a projected lens mass of $M(<250~\mathrm{kpc}) = 1.21^{+0.09}_{-0.04} \times 10^{14}~M_\odot$, an Einstein radius of $θ_\mathrm{E} = 10.8^{+0.3}_{-0.4}~\mathrm{arcsec}$, and a total effective magnification of $μ_\mathrm{tot}=24.2^{+3.4}_{-1.2}$ for the giant arc. Across the arc, individual clump magnifications span $μ_\mathrm{clump}\sim4-19$, with fractional magnification uncertainties of $σ_μ/|μ_{\rm best}|\sim0.03-0.09$. We report a $\sim2-8\times$ improvement in magnification precision over previous models. Ongoing and future analyses of this arc will enable robust measurements of star-forming structure, building on the lensing foundation established here for LEGGOS studies of galaxy growth and feedback during cosmic noon.

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arXiv2026

COOL-LAMPS IX: A Rare Duo of Quasars Each Lensed by a Single Massive Galaxy Cluster

Wide-separation lensed quasars (WSLQs) are rare systems that arise from the chance alignment of two objects: a galaxy cluster and a background quasar. After two decades, only seven WSLQs have been found. Here, we report the discovery of COOLJ1153+0755 by the COOL-LAMPS collaboration in DECaLS imaging and its confirmation with follow-up observations with the Magellan Telescopes and the Nordic Optical Telescope. This system features two multiply-imaged quasars each lensed into four images by the same $z=0.4301$ cluster: a classic broad-line Type I quasar at $z=1.524$ (COOLJ1153A) and a dust-obscured Type II quasar at $z=1.939$ (COOLJ1153B), with maximum image separations of $25.''6$ and $26.''0$, respectively. We construct a lens model to estimate a projected cluster mass of $M(<500\,{\rm kpc})\sim3.3\times10^{14}{\rm M}_{\odot}$ and relative time delays between the three brightest images of each quasar of $Δt_{\rm \,A3,A1}\sim800$, $Δt_{\rm \,A2,A1}\sim1200$, $Δt_{\rm \,B1,B3}\sim800$, and $Δt_{\rm \,B2,B3}\sim1000$ days. COOLJ1153A resides in a dense environment with three nearby galaxies, two of which are also strongly lensed. We identify COOLJ1153+0755 without making a morphological cut in the DECaLS catalog; none of its multiple images are classified as point sources in those data, implying that morphology-based selection would miss such systems. COOLJ1153+0755 expands the WSLQ sample from 7 to 8 systems (9 individual quasars), adding two powerful laboratories for probing black hole-galaxy co-evolution at Cosmic Noon and for time-delay cosmography constraints on the Hubble constant, $H_0$.

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arXiv2026

Strong LensIng and Cluster Evolution (SLICE) with JWST: Early Results, Lens Models, and High-Redshift Detections

We leverage JWST's superb resolution to derive strong lensing mass maps of 14 clusters, spanning a redshift range of $z\sim0.25 - 1.06$ and a mass range of $M_{500}\sim2-12 \times 10^{14}M_\odot$, from the Strong LensIng and Cluster Evolution (SLICE) JWST program. These clusters represent a small subsample of the first clusters observed in the SLICE program that are chosen based on the detection of new multiple image constraints in the SLICE-JWST NIRCam/F150W2 and F322W2 imaging. These constraints include new lensed dusty galaxies and new substructures in previously identified lensed background galaxies. Four clusters have never been modeled before. For the remaining 10 clusters, we present updated models based on JWST and HST imaging and, where available, ground-based spectroscopy. We model the global mass profile for each cluster and report the mass enclosed within 200 and 500 kpc. We report the number of new systems identified in the JWST imaging, which in one cluster is as high as 19 new systems. The addition of new lensing systems and constraints from substructure clumps in lensed galaxies improves the ability of strong lensing models to accurately reproduce the interior mass distribution of each cluster. We also report the discovery of a candidate transient in a lensed image of the galaxy cluster SPT-CL J0516-5755. All lens models and their associated products are available for download at the Strong Lensing Cluster Atlas Data Base, which is hosted at Laboratoire d'Astrophysique de Marseille.

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arXiv2026

Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters

The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $\sim 10$\% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $6~h^{-1}\rm{Mpc}$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $6~h^{-1}\rm{Mpc}$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term.

astro-ph.CO↗

arXiv2026

A Kiloparsec-Scale Stellar Cavity in the Center of Abell402-BCG May be Caused by Dynamic Interactions with an Ultramassive Black Hole

We present new observations from JWST NIRCam that reveal a striking kpc-wide cavity in the stellar distribution of the central galaxy in the cluster Abell402. Supporting data from HST allow us to rule out extinction due to dust as an explanation and, instead, suggest that this is a localized depression in the stellar density field corresponding to ~2x10^9 Msun in missing stars within a volume of 0.5kpc^3. On larger scales, both the JWST and HST data show evidence for a 2.2kpc flattened core in the stellar distribution (on which the smaller-scale cavity is superimposed), which implies the presence of a central ultra-massive black hole with M_BH = 6 +/- 4 x10^10 Msun. We report evidence for a mid-IR-bright point source at one edge of the cavity, suggesting that this black hole is actively accreting. MUSE spectroscopy reveal that this source is a LINER AGN and that there is a second candidate AGN on the opposite side of the cavity with a relative velocity of 370km/s -- if real, this implies the presence of a kpc-separation dual AGN with a total binary mass of 6 +/- 2 x10^10 Msun, which would make this the most massive binary black hole system discovered to date. We propose that this unique stellar cavity is the result of a short-lived dynamical interaction between at least one supermassive black hole and the background stellar density field, caused either by three-body scattering during binary hardening or the induction of a dipole instability in the stellar density field.

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arXiv2026

The Sunburst Arc with JWST. IV. The importance of interaction, turbulence, and feedback for Lyman-continuum escape

At present, the best opportunity for detailed Lyman Continuum escape studies is in gravitationally lensed galaxies at z >~ 2. Only one such galaxy currently exists in the literature with sufficient spatial magnification: The Sunburst Arc at redshift z = 2.37. Here, we present rest-frame optical JWST NIRSpec integral field observations of the Sunburst Arc that cover a large fraction of the source plane. From this dataset, we generate precise maps of ISM kinematics, dust geometry, ionization, and chemical enrichment. We extract a stacked spectrum of five gravitationally lensed images of the Lyman-Continuum leaking cluster, as well as an magnification-corrected, integrated spectrum of most of the galaxy, enabling a direct comparison to other LyC leakers in the literature. We find that the galaxy rotates but also shows strong, possibly dominant, signatures of turbulence, which are indicative of recent or ongoing major interaction. The cluster that leaks ionizing photons shows little variation in kinematics or dust coverage, but dramatically elevated ionization, indicating that photoionization is the predominant mechanism that creates paths for LyC escape. We conjecture that tidal stripping of H I gas due to an interaction could have removed a large portion of the neutral ISM around the LyC emitting cluster, making it easier for the cluster to completely ionize the rest.

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arXiv2025

JWST & the Waz Arc I: Spatially Resolving the Physical Conditions within a Post-Starburst Galaxy at Redshift 5 with NIRSpec IFS

We present NIRSpec/IFS observations of a rest-frame UV-bright, massive ($M_* \sim 10^{10}$ M$_\odot$, $z_{AB}=20.5$) galaxy highly magnified by gravitational-lensing observed just after the end of the epoch of reionization ($z=5.04$, $\barμ\sim90$). With JWST accessing the restframe UV and optical spectrum of this galaxy with high fidelity, we classify this UV-bright galaxy as post-starburst in nature -- due to weak/absent emission lines and strong absorption features -- making this an example of a new class of UV-bright but significantly quenched galaxies being discovered in this epoch. With a median $E(B-V)=0.44\pm0.14$, we identify the presence of stellar absorption across the arc both in Balmer lines and the MgII doublet, indicative of older stellar populations dominated by A stars (and potentially B stars). Using spatially-resolved maps of rest-optical strong emission lines, we find a heterogeneous distribution of nebular metallicities across the arc, potentially hinting at different enrichment processes. With a low median lensing-corrected H$α$ star formation rate of SFR$_{Hα} = 0.024 \pm 0.001$ M$_\odot$ yr$^{-1}$, we find in the most "star-forming" clumps indications of lower ionization (log$_{10}$U $\sim -3.2$), lower nebular metallicities (12+log$_{10}$O/H $\lesssim$ 8.3), and hints of higher densities that suggest a possible recent infall of more pristine (low metallicity) gas onto the galaxy. Investigating the regions with no detectable H$β$ emission, we find (for the first time at $z>5$) signatures of diffuse ionized gas (DIG). Separating DIG from HII regions within a galaxy has predominantly been demonstrated at lower redshifts, where such spatial resolution allows clear separation of such regions -- highlighting the immense power of gravitational lensing to enable studies at the smallest spatial scales at cosmic dawn.

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arXiv2025

Tracing Structure: Shape and Centroid Deviations in 39 Strong Lensing Clusters as a Test of Cluster Formation Predictions

Strong lensing galaxy clusters provide a unique and powerful way to test simulation-derived structure predictions that follow from $Λ$ Cold Dark Matter ($Λ$CDM) cosmology. Specifically, the relative alignments of the dark matter (DM) halo, stars, and hot intracluster gas in these clusters offer insights into how well theoretical structure predictions hold. We measure the position angles, ellipticities, and locations/centroids of the brightest cluster galaxy (BCG), the Intracluster Light (ICL), the hot Intracluster Medium (ICM), and the Core Lensing Mass (CLM) for a sample of strong lensing galaxy clusters from the Sloan Giant Arcs Survey (SGAS). We measure the shapes (position angles and ellipticities) and centroids of these distributions using ellipse-fitting methods applied to different datasets: HST WFC3 imaging for the BCG and ICL, Chandra X-ray observations for the ICM, and strong-lensing mass reconstructions for the CLM. Additionally, we incorporate ICM morphological measures to classify the dynamical state of the cluster sample. Using this multi-component approach, we constrain the shape and centroids of these distributions in this sample and evaluate the different observable components in terms of their ability to trace the gravitational potential of their respective clusters. We find that misalignments between cluster components can be explained by astrophysical processes related to cluster assembly, relaxation, and merger histories. We find that the ICL is most closely aligned with its host DM halo, as traced by the CLM distribution, in both position angle and centroid. Additionally, we find that on average the ICL and CLM are more elliptical than the ICM and BCG.

astro-ph.CO↗

arXiv2025

The Chandra Strong Lens Sample: Measuring the Dynamical States and Relaxation Fraction of a Sample of 28 Strong Lensing Selected Galaxy Clusters

We present the results of our dynamical state proxy measurements performed on 28 strong lensing galaxy clusters from the Sloan Giant Arcs Survey (SGAS). Using Chandra ACIS-I/S X-ray data supplemented with HST WFC3 imaging, we measure four morphological parameters: the concentration parameter (c), asymmetry parameter (A), centroid shift (log(w)), and the X-ray-BCG centroid separation (D [kpc]). Our goals are to (A) provide a robust classification of the dynamical state of the clusters in this strong lensing selected sample to enable studies that test various problems in cluster astrophysics and observational cosmology; (B) identify correlations, biases, or disagreements between different measurement proxies and cluster properties; and (C) measure the relaxation fraction (the fraction of clusters classified as relaxed based on X-ray morphology) and compare it to relaxation fractions from cluster samples selected using other methods. We combine the four morphological parameters into a single metric, the combined parameter M, which effectively separates the cluster sample into four dynamical state categories: relaxed; moderately relaxed; moderately disturbed; and disturbed. We find no significant trend in a cluster's dynamical state with its size, and only a weak, statistically limited dependence on mass and redshift. Based on our classification system, we find that $43\%^{+9}_{-9}$ of the clusters are relaxed, which is consistent with relaxation fractions measured for other cluster samples selected on mass-observables. This implies a strong lensing selected sample of clusters is on average dynamically similar to clusters selected via different methods.

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arXiv2025

SLICE: SPT-CL J0546-5345 -- A prominent strong-lensing cluster at $z=1.07$

Massive galaxy clusters act as prominent strong-lenses. Due to a combination of observational biases, cluster evolution and lensing efficiency, most of the known cluster lenses lie typically at $z_{l}\sim0.2-0.7$, with only a few prominent examples at higher redshifts. Here we report a first strong-lensing analysis of the massive galaxy cluster SPT-CL J0546-5345 at a redshift $z_l=1.07$. This cluster was first detected through the Sunyaev-Zel'dovich effect, with a high estimated mass for its redshift of $M_{200,c} = (7.95 \pm 0.92) \times 10^{14}\,M_{\odot}$. Using recent JWST/NIRCam and archival HST imaging, we identify at least 10 secure and 6 candidate sets of multiply imaged background galaxies, which we use to constrain the mass distribution in the cluster. We derive effective Einstein radii of $θ_{E}= 18.1 \pm 1.8 ''$ for a source at $z_{s}=3$, and $θ_{E}= 27.9 \pm 2.8 ''$ for a source at $z_{s}=9$. The total projected mass within a $200$ kpc radius around the strong-lensing region is $M(<200\,\mathrm{kpc}) = (1.9 \pm 0.3) \times 10^{14}\,M_{\odot}$. While our results rely on photometric redshifts warranting spectroscopic follow-up, this central mass resembles that of the Hubble Frontier Fields clusters - although SPT-CL J0546-5345 is observed when the Universe was $\sim 3-4$ Gyr younger. Amongst the multiply-imaged sources, we identify a hyperbolic-umbilic-like configuration, and, thanks to its point-like morphology, a possible Active Galactic Nucleus (AGN). If confirmed spectroscopically, it will add to just a handful of other quasars and AGN known to be multiply lensed by galaxy clusters.

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arXiv2025

The z=1.03 Merging Cluster SPT-CL J0356-5337: New Strong Lensing Analysis with HST and MUSE

We present a strong lensing analysis and reconstruct the mass distribution of SPT-CL J0356-5337, a galaxy cluster at redshift z = 1.034. Our model supersedes previous models by making use of new multi-band HST data and MUSE spectroscopy. We identify two additional lensed galaxies to inform a more well-constrained model using 12 sets of multiple images in 5 separate lensed sources. The three previously-known sources were spectroscopically confirmed by Mahler et al. (2020) at redshifts of z = 2.363, z = 2.364, and z = 3.048. We measured the spectroscopic redshifts of two of the newly-discovered arcs using MUSE data, at z = 3.0205 and z = 5.3288. We increase the number of cluster member galaxies by a factor of three compared to previous work. We also report the detection of extended Lya emission from several background galaxies. We measure the total projected mass density of the two major sub-cluster components, one dominated by the BCG, and the other by a compact group of luminous red galaxies. We find M_BCG(< 80kpc) = 3.93+0.21-0.14 * 10^13Msun and M_LRG(< 80kpc) = 2.92+0.16 -0.23 * 10^13Msun, yielding a mass ratio of 1.35+0.16 -0.08. The strong lensing constraints offer a robust estimate of the projected mass density regardless of modelling assumptions; allowing more substructure in this line of sight does not change the results or conclusions. Our results corroborate the conclusion that SPT-CL J0356-5337 is dominated by two mass components, and is likely undergoing a major merger on the plane of the sky

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arXiv2025

Intergalactic Medium Tomography with the Sunburst Arc

Gravitational lensing has transformed the field of gas tomography in the intergalactic medium (IGM) and circumgalactic medium (CGM). Here we use the brightest lensed galaxy identified to date, the Sunburst Arc ($z$$\approx$2.37), to constrain the physical size of foreground absorbers at $z$$\approx$2 in 2D. This galaxy is a confirmed Lyman continuum leaker, where its single leaking region is imaged 12 times over four separate arcs. The separations between the arcs allows for large scale tomography, while the distances between the images along an arc allow for small scale tomography. Using HST/WFC3 UVIS G280 grism observations, we extracted the spectra of the leaking region and fit for absorbers detected along these lines of sight using a binary population and spectral synthesis (BPASS) model for the galaxy. We identified two partial Lyman limit systems (pLLSs) and one Lyman limit system (LLS) across the different spectra and measured their physical sizes. We find consistent HI column densities across $\lesssim$2 kpc and an average HI mass of $\approx$10$^3$ ${\rm M}_\odot$ for the absorbers. Given the strong CIV lines associated with two of the absorbers, they are likely located within the CGM of foreground galaxies. The third absorber has no associated metal lines, so it is most likely within the IGM. This study provides the first tomography measurements of pLLSs/LLSs in the CGM and IGM at $z$$\approx$2.

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arXiv2025

Deciphering spatially resolved Lyman-alpha profiles in reionization analogs: the Sunburst Arc at cosmic noon

The hydrogen Lyman-alpha (Lya) emission line, the brightest spectral feature of a photoionized gas, is considered an indirect tracer of the escape of Lyman continuum (LyC) photons, particularly when the intergalactic medium is too opaque for direct detection. However, resonant scattering complicates interpreting the empirical properties of Lya photons, necessitating radiative transfer simulations to capture their strong coupling with underlying gas kinematics. In this study, we leverage the exceptional spatial resolution from strong gravitational lensing to investigate the connection between Lya line profiles and LyC leakage on scales of a few 100 pc in the Sunburst Arc galaxy at $z\!\sim\!2.37$. New optical echelle spectra obtained using Magellan MIKE show that both the LyC leaking and non-leaking regions exhibit a classic double-peak Lya feature with an enhanced red peak, indicating outflows at multiple locations in the galaxy. Both regions also show a central Gaussian peak atop the double peaks, indicating directly escaped Lya photons independent of LyC leakage. We introduce a machine learning-based method for emulating Lya simulations to quantify intrinsic dynamics ($σ_{\mathrm{int}}$), neutral hydrogen column density ($N_{\mathrm{HI}}$), outflow velocity ($v_{\mathrm{exp}}$), and effective temperature ($T$) across continuous parameter spaces. By comparing the spatially and spectrally resolved Lya lines in Sunburst, we argue that the directly escaped Lya photons originate in a volume-filling, warm ionized medium spanning $\sim\!1$ kpc, while the LyC leakage is confined to regions of $\lesssim\!200$ pc. These sub-kpc variations in Lya profiles highlight the complexity of interpreting integrated properties in the presence of inhomogeneous mixtures of gas and young stars, emphasizing the need for spatially and spectrally resolved observations of distant galaxies.

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arXiv2025

COOL-LAMPS. VII. Quantifying Strong-lens Scaling Relations with 177 Cluster-scale Strong Gravitational Lenses in DECaLS

We estimate the Einstein-radius-enclosed total mass for 177 cluster-scale strong gravitational lenses identified by the ChicagO Optically selected Lenses Located At the Margins of Public Surveys (COOL-LAMPS) collaboration with lens redshifts ranging from $0.2 \lessapprox z \lessapprox 1.0$ using the brightest-cluster-galaxy (BCG) redshift and an observable proxy for the Einstein radius. We constrain the Einstein-radius-enclosed luminosity and stellar mass by fitting parametric spectral energy distributions to aperture photometry from the Dark Energy Camera Legacy Survey in the $g$-, $r$-, and $z$-band Dark Energy Camera filters. We find that the BCG redshift, enclosed total mass, and enclosed luminosity are strongly correlated and well described by a planar relationship in 3D space. We find that the enclosed total mass and stellar mass are correlated with a logarithmic slope of $0.500^{+0.029}_{-0.031}$, and the enclosed total mass and stellar-to-total mass fraction are correlated with a logarithmic slope of $-0.495^{+0.032}_{-0.033}$. In tandem with the small radii within which these slopes are constrained, this may suggest invariance in baryon conversion efficiency and feedback strength as a function of cluster-centric radii in galaxy clusters. Additionally, the correlations described here should have utility in ranking strong-lensing candidates in upcoming imaging surveys -- such as Rubin/Legacy Survey of Space and Time -- in which an algorithmic treatment of strong lenses will be needed due to the sheer volume of data these surveys will produce.

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arXiv2025

Strong Lensing analysis of SPT-CLJ2325$-$4111 and SPT-CLJ0049$-$2440, two Powerful Cosmic Telescopes ($R_E > 40''$) from the SPT Clusters Sample

We report the results from a study of two massive ($M_{500c} > 6.0 \times 10^{14} M_{\odot}$) strong lensing clusters selected from the South Pole Telescope cluster survey for their high Einstein radius ($R_E > 40''$), SPT-CLJ2325$-$4111 and SPT-CLJ0049$-$2440. Ground-based and shallow HST imaging indicated extensive strong lensing evidence in these fields, with giant arcs spanning 18\arcsec\ and 31\arcsec, respectively, motivating further space-based imaging followup. Here, we present multiband HST imaging and ground-based Magellan spectroscopy of the fields, from which we compile detailed strong lensing models. The lens models of SPT-CL\,J2325$-$4111 and SPT-CL\,J0049$-$2440 were optimized using 9, and 8 secure multiple-imaged systems with a final image-plane rms of 0\farcs63 and 0\farcs73, respectively. From the lensing analysis, we measure the projected mass density within 500~kpc of $M(<500 ~{\rm kpc}) = 7.30\pm0.07 \times 10^{14}$$M_{\odot}$, and $M(<500 ~{\rm kpc})=7.12^{+0.16}_{-0.19}\times 10^{14}$ $M_{\odot}$ for these two clusters, and a sub-halos mass ratio of $0.12\pm{0.01}$ and $0.21^{+0.07}_{-0.05}$, respectively. Both clusters produce a large area with high magnification ($μ\geq 3$) for a source at $z=9$, $A^{lens}_{| μ| \geq 3 }=4.93^{+0.03}_{-0.04} arcmin^2$, and $A^{lens}_{| μ| \geq 3 }=3.64^{+0.14}_{-0.10} arcmin^2$ respectively, placing them in the top tier of strong lensing clusters. We conclude that these clusters are spectacular sightlines for further observations that will reduce the systematic uncertainties due to cosmic variance. This paper provides the community with two additional well-calibrated cosmic telescopes, as strong as the Frontier Fields, suitable for studies of the highly magnified background Universe.

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