arXiv subjects

Glenn G. Kacprzak

Publications and source records attributed to Glenn G. Kacprzak.

At least 19 recordsLinked to original sources

arXiv2026

The Carousel Lens I: A Spectroscopic Survey of the Carousel Lens Field

We present a spectroscopic survey of field galaxies and lensed sources in the vicinity of the strong lensing galaxy cluster known as the Carousel lens at z=0.49. Using both Gemini/GMOS slitmask spectra and deep VLT/MUSE observations, we bring the total number of lensed sources up to 12, including three which were not previously known from imaging observations but are apparent in the MUSE data as emission-line sources. Of these sources, 10 have confident redshifts, and an additional 2 have tentative redshifts from likely Ly$α$ emission (including seven new redshifts determined here adding to those presented previously in \cite{Sheu.Cikota.ea2024}). In total, we identify 42 images of these 12 sources. This lens system is remarkably symmetric and well-modeled by a simpler lens model than typical cluster lenses, and the large number of sources and their large range of redshifts make this cluster ideal for constraining cosmological parameters such as $w$ and $Ω_m$ as well as the cluster density profile. Additionally, we present a catalog of 57 unlensed field galaxies with confident redshifts, of which 49 are associated with the cluster. We measure a cluster velocity dispersion of about 1100 km s$^{-1}$ from which we estimate a halo mass $M_{200c} \sim 1.2 \times 10^{15} M_\odot$.

astro-ph.GA↗

arXiv2026

Circumgalactic CIV Absorption Found Only Within 30 Degrees of the Minor Axis of Present-Epoch Galaxies

We studied CIV 1548,1550 absorption in the circumgalactic medium (CGM) of 88 isolated, bright (L_B > 0.2L*_B) galaxies at z < 0.03 selected without prior knowledge of CGM absorption. The galaxies have observationally-unbiased distributions of inclination and galaxy-quasar sightline azimuthal angle. Above a 5-sigma rest-frame equivalent width detection threshold of W_r > 0.1 angstroms, we found absorption in the CGM of 9/88 of the galaxies within projected separation R_perp < 350 kpc. All nine absorbers arise within 30 deg of the projected minor axes and R_perp < 1.2R_vir of star-forming galaxies [log(sSFR/yr^-1) > -10.75]. To a confidence level of 99.998% (4.3-sigma), we can rule out that these absorbers are drawn from a random distribution of galaxy-quasar azimuthal angles. These findings suggest strong evidence for biconical polar winds related to the moderately elevated star formation in these present-epoch galaxies and we describe simple spatial-kinematic models that support this hypothesis. High specific star-formation rates may not be a sufficient condition for predicting minor-axis CIV absorption because the covering fraction of the subsample of star-forming galaxies within 30 deg of their minor axes is f_cov ~ 0.5; this may imply transient and/or patchy outflows. Incorporating studies of MgII and OVI CGM absorption, we favor a scenario in which CIV-bearing CGM gas interfaces between these low- and high-ionization regimes, comprising enriched intermediate-ionization clouds entrained and collimated in biconical stellar winds while mixing and cooling via non-equilibrium photoionization.

astro-ph.GA↗

arXiv2026

An emerging baryon cycle in a galaxy 500 million years after the Big Bang

The emergence of stellar feedback as a regulator of galaxy growth marks a fundamental transition in cosmic history. At early times, rapid gas accretion and collapse may induce intense star formation before feedback becomes effective, producing feedback-free starbursts. When and how such bursts subsequently develop into self-regulated baryon cycles remain observationally unknown. Here we show that Gz9p3, a merging galaxy at $z=9.311$, is caught in this transition only 500 million years after the Big Bang. Deep JWST spectroscopy reveals a substantial neutral-gas reservoir along its merger-driven tidal structure and a multiphase outflow. Fine-structure absorption provides the first direct measurement of the electron density of the cool outflowing gas at high redshift ($\approx\,17\,{\rm cm^{-3}}$), yielding a mass-loading factor among the highest yet measured for galaxies of comparable stellar mass. The emergence of such efficient feedback after an intense burst is consistent with the delayed onset of feedback expected in feedback-free starburst models. The cool outflowing gas is unlikely to escape the host halo, implying that much of this metal-enriched material may remain available for future recycling through the circumgalactic medium. Gz9p3 therefore provides an early view of a baryon cycle being established through the interplay of merger-driven gas redistribution, bursty star formation and stellar feedback, suggesting that feedback-regulated recycling was already shaping galaxy growth during the epoch of reionization.

astro-ph.GA↗

arXiv2026

The chemodynamical signature of coherent metal-poor inflow and enriched recycled accretion in the cool circumgalactic medium

The azimuthal and kinematic structure of the CGM is often interpreted as planar accretion and bipolar outflows, yet direct metallicity evidence for this picture remains ambiguous. We combine cloud-by-cloud ionisation modelling with galaxy rotation kinematics for 21 galaxies from the Multiphase Galaxy Halos Survey to investigate how metallicity depends on azimuthal angle and angular momentum. We find that low-ionisation clouds kinematically consistent with disk rotation have ~0.5 dex lower metallicity near the projected major axis ($Φ<30^\circ$) than at larger azimuthal angles. Major-axis clouds also exhibit higher N(HI), higher density, and reduced non-thermal line broadening compared to clouds at larger azimuthal angles. In contrast, the higher-ionisation phase shows no significant metallicity dependence on azimuthal angle and has lower column densities, lower densities, higher temperatures, and broader line widths than the co-rotating major-axis low-ionisation clouds. These combined metallicity--kinematic--ionisation signatures are consistent with dynamically cold, metal-poor inflow along the disk plane and enriched, more turbulent gas at larger azimuthal angles that likely traces angular-momentum-supported recycled accretion, embedded within a dynamically complex warmer phase. These results show that metallicity and angular momentum are jointly imprinted by the baryon cycle and are both required to uncover the physical origins of CGM gas.

astro-ph.GA↗

arXiv2026

Revealing Cosmic Ecosystems with the Hubble Space Telescope in 2030s and Beyond

Ultraviolet spectroscopy with the Hubble Space Telescope (HST) provides the most direct and sensitive probe of the disk-circumgalactic medium (CGM) interface at radii of 20 kpc, where galaxies exchange gas, metals, and energy with their surroundings. Many of the key diagnostics of the multiphase circumgalactic medium -- including H I, O VI, C II-IV, Si II-IV, N V, Ne VIII, and other metal transitions -- lie in the ultraviolet and are inaccessible from the ground, making HST the only observatory capable of making the required observations. By measuring the physical (column density, density), chemical (metallicity, ionization structure), and kinematical properties of the gas at the disk-CGM interface, UV absorption-line spectroscopy reveals how galaxies acquire fresh fuel, recycle enriched material, and drive feedback into their halos. When combined with spectroscopic characterization of the host galaxy's stellar populations and the feedback they generate (outflow velocity, mass loading), we will establish a direct understanding of how stellar populations enable circulation of gas and metals through the galactic ecosystem. HST's ultraviolet (UV) spectroscopic capability provides the only comprehensive observational pathways for uncovering the physical drivers that regulate galaxy growth and evolution in the low-redshift Universe.

astro-ph.IM↗

arXiv2026

Most Strong Lensing Deflectors in the AGEL Survey Are in Group and Cluster Environments

The environments of deflectors in strong lensing systems affect our ability to test cosmological models and constrain evolutionary properties of galaxies. Here we measure the deflector scale (Einstein mass) and deflector environment (halo mass) of 89 spectroscopically confirmed strong lenses in the ASTRO3D Galaxy Evolution With Lenses (AGEL) survey. We classify deflector scale by measuring $θ_{\rm{E}}$ to determine the mass enclosed by the Einstein radius, $M(<θ_{\rm{E}})$. We quantify deflector environment by using photometric redshifts to determine the galaxy surface density to the fifth-nearest neighbor $Σ_5(z)$. We find that 47.2% of our deflectors are embedded in cluster environments, whereas only 9.0% have cluster-scale Einstein radii (masses). We measure a weak correlation ($r = 0.38$) between Einstein mass and $Σ_5(z)$, suggesting that the assumption of single galaxy-scale deflectors in lens modeling is overly-simplified. We hypothesize that the weak correlation results from galaxy-scale bias in the original AGEL selection and the observational challenge of detecting faint arcs with large Einstein radii. Comparing number densities, $N_{\rm{gal}}$, between AGEL and control fields, we find that AGEL deflectors are in systematically denser environments. Our study provides a method to identify strong lenses as a function of deflector environment and approximate the impact of large-scale environment in lens modeling. We provide the measured lensing parameters for our 89 AGEL systems as well as $z_{\rm{phot}}$ and $r$-mag (AB) maps of the line-of-sight.

astro-ph.GA↗

arXiv2026

The Carousel Lens II: Cosmological Constraints with GIGA-Lens

The nature of dark matter and dark energy are among the central questions in cosmology. Strong gravitational lenses with multiple source planes provide a geometric probe of cosmology: the ratio of deflection angles at different redshifts depends only on angular-diameter distances, constraining the matter density $Ω_m$ and the dark energy equation of state $w$. However, constraints from this technique have historically lagged behind those from the CMB, SNe Ia, and BAO. In this work, we present new cosmological constraints from the Carousel Lens, a cluster-scale lens with more than 40 extended images from 11 spectroscopically confirmed sources. Its relaxed core and rich set of extended images behind the main halo make it particularly suitable for cosmological inference. Using the GIGA-Lens pipeline, we construct a pixel-level lens model including six HST-detected sources and four mass components. From this model, we obtain $w$CDM constraints of $Ω_m = 0.34^{+0.16}_{-0.13}$ and $w = -1.31^{+0.35}_{-0.32}$ from the Carousel Lens alone, accounting for both statistical and systematic uncertainties. We further project that including four additional known higher-redshift sources, assuming similar fractional uncertainties, could improve the constraining power by ~80%, bringing the precision close to that of the CMB and SNe Ia. For an evolving dark energy model ($w_0w_a$CDM), the Carousel Lens alone yields constraints comparable to the CMB, providing an independent and complementary probe alongside SN Ia and BAO. While currently systematic uncertainties dominate, which we quantify through simulations, our results demonstrate that relaxed multi-source-plane cluster lenses can deliver competitive cosmological constraints. Further improvements are expected from reductions in systematics and from incorporating higher-redshift sources (known and new) with high-resolution imaging.

astro-ph.CO↗

arXiv2026

Multi-band Reconstruction of Sixteen Gravitational Lens Systems using PISCO data

Next-generation surveys such as the Euclid survey, the Legacy Survey of Space and Time (LSST), and the China Space Station Telescope (CSST) survey are expected to discover ~10^5 galaxy-galaxy scale strong gravitational lenses. This motivates the development of scalable and robust lens modeling approaches that can efficiently and reliably learn from wide-field survey datasets before high-resolution follow-up. We design a scalable, Bayesian, Lenstronomy-based pipeline and apply it to a sample of sixteen lens candidates observed with the Parallel Imager for Southern Cosmology Observations (PISCO) on the Magellan telescope. PISCO provides four-band imaging (z, i, r, g) with colours, depth and seeing conditions comparable to LSST. To fully exploit the constraining power of this dataset, our pipeline performs simultaneous multi-band modeling, using a common mass profile across all four bands while allowing independent light profiles in each. This approach leverages color information to provide joint constraints on the lens mass and yields reduced uncertainties compared to single-band analyses. Fifteen out of sixteen PISCO lens candidates are successfully recovered with interpretable lensing configurations, including DESJ0533-2536, the first reported hyperbolic-umbilic galaxy-galaxy scale strong lensing candidate. We further assess how much model complexity can be reliably constrained given the resolution and seeing of PISCO-like data. Overall, our results demonstrate that scalable, multi-band lens modeling of ground-based data can extract meaningful constraints on mass and source morphology, providing a practical pathway to maximize the scientific return from large samples in upcoming surveys.

astro-ph.GA↗

arXiv2025

Kinematics of Circumgalactic O VI Gas and Disk Rotation of $z\approx0.2$ Star-forming Galaxies

Quasar sightline observations reveal that low-ionization-state gas corotates with the galaxy disk and often at sub-centrifugal velocities, suggesting that the gas is spiraling towards the galaxy disk. However, while observations ubiquitously detect O VI absorption around low-redshift, $\sim L^*$ star-forming galaxies, the relationship between O VI and the galaxy disk, especially the kinematics, is not well-established. This work focuses on the O VI kinematics and its comparison with that of the low ions and galactic disk rotation. We present observations of 18 pairs of quasars and $z\approx0.2$ star-forming galaxies. All quasar sightlines intersect the circumgalactic medium (CGM) within 45$^\circ$ from the galaxy major axes. We show that while individual O VI velocity components do not correlate with disk rotation, the bulk of O VI gas in individual sightlines rarely counter-rotates. We then match O VI velocity components with those of low ions by minimizing the difference of their velocity centroids. The O VI velocity components with successful low-ion matches are typically found at small sightline impact parameters and are more likely to corotate with the disk. We suggest that the low-ion-matched O VI velocity components trace the gas co-spatial with the low ions near the extended disk plane in the inner CGM, whereas those without low-ion matches represent the gas at large 3D radii. While the gas at large radii is theoretically expected to kinematically correlate with the disk angular momentum, this correlation is expected to be weaker due to the higher turbulent to mean rotation velocity ration at large radii, consistent with our results.

astro-ph.GA↗

arXiv2025

Constraining Cosmology with Double-source-plane Strong Gravitational Lenses from the AGEL Survey

Double-source-plane strong gravitational lenses (DSPLs), with two sources at different redshifts, are independent cosmological probes of the dark energy equation of state parameter $w$ and the matter density parameter $Ω_{\rm m}$. We present the lens model for the DSPL AGEL035346$-$170639 and infer cosmological constraints from this system for flat $Λ$ cold dark matter and flat $w$CDM cosmologies. From the joint posterior of $w$ and $Ω_{\rm m}$ in the flat $w$CDM cosmology, we extract the following median values and 1$σ$ uncertainties: $w = -1.52^{+0.49}_{-0.33}$ and $Ω_{\rm m} = 0.192^{+0.305}_{-0.131}$ from AGEL0353 alone. Combining our measurements with two previously analyzed DSPLs, we present the joint constraint on these parameters from a sample of three, the largest galaxy-scale DSPL sample used for cosmological measurement to date. The combined precision of $w$ from three DSPLs is higher by 15% over AGEL0353 alone. Combining DSPL and cosmic microwave background (CMB) measurements improves the precision of $w$ from CMB-only constraints by 39%, demonstrating the complementarity of DSPLs with the CMB. Despite their promising constraining power, DSPLs are limited by sample size, with only a handful discovered so far. Although ongoing and near-future wide-area sky surveys will increase the number of known DSPLs by up to two orders of magnitude, these systems will still require dedicated high-resolution imaging and spectroscopic follow-ups like those presented in this paper. Our ASTRO 3D Galaxy Evolution with Lenses collaboration is undertaking such follow-up campaigns for several newly discovered DSPLs and will provide cosmological measurements from larger samples of DSPLs in the future.

astro-ph.CO↗

arXiv2025

13 Billion Years of MgII Absorber Evolution

Applying "apportioned integrals," we use dN/dX measurements to determine the MgII absorber equivalent width distribution function for Wr > 0.03 [angstroms] and 0 < z < 7. Adopting a Schechter distribution, f(z,W)dW = Phi* (W/W*)^alpha e^{-W/W*} dW/W*, we present the normalization, Phi*(z), the characteristic equivalent width, W*(z), and the weak-end slope, alpha(z), as smooth functions of redshift. Measurements of dN/dX are robust for z < 4 but less so at z > 4 for weaker absorbers (Wr < 0.3 [angstroms]). We bracketed two data-driven scenarios: from z ~ 7 to z ~ 4, dN/dX of weak absorbers is (1) constant, or (2) decreasing. For scenario #1, the evolution of Phi*(z), W*(z), and alpha(z) show that in the post-reionization universe, weak systems are nonevolving while the incidence of the strongest systems increases until Cosmic Noon; following Cosmic Noon, the strongest absorbers slowly evolve away while the incidence of weak absorbers rapidly increases. For scenario #2, the parameter evolution is such that, in the post-reionization universe, weak systems evolve away while the incidence of the strongest systems increases until Cosmic Noon; following Cosmic Noon, the behavior tracks the same as scenario #1. We argue in favor of scenario #2 based on corroborating OI, CII, and SiII measurements at z > 4. Our results provide a unified, quantitative description for MgII absorber evolution spanning 13 billion years of cosmic time and offer deeper insights into galactic baryon cycle physics. They also highlight the need for deep z > 5 MgII surveys and have implications for detectability of a MgII forest at z > 7.

astro-ph.CO↗

arXiv2025

Ultra-strong MgII absorbers trace both inflowing and outflowing gas: insights from dual down-the-barrel and quasar sightlines

We present Keck/LRIS spectroscopy of seven isolated galaxy-quasar pairs at $0.4 \leq z \leq 0.6$, each exhibiting ultra-strong MgII absorption ($W_{r,2796} \geq 3$ Å), probing both down-the-barrel and transverse gas flows. Down-the-barrel galaxy spectra reveal outflows in three galaxies ($v = 19$ to $311$ km s$^{-1}$) and inflows in five ($v = 61$ to $361$ km s$^{-1}$), including one system showing inflows and outflows simultaneously. All galaxies with detected inflows are below the star-forming main sequence, suggesting that they might be actively replenishing their gas reservoirs. Outflows have a mean covering fraction of $C_{f, \rm out}=0.5$, whereas inflows show a lower average of $C_{f, \rm in}=0.3$. Mass flow rates span $\dot{M}_{\rm in} = 0.01-1.18$ $M_{\odot} \mathrm{yr}^{-1}$ for inflows and $\dot{M}_{\rm out} = 0.23-1.03$ $M_{\odot}\mathrm{yr}^{-1}$ for outflows, yielding mass loading factors below unity and implying these galaxies cannot sustain their current level of star-formation rates. These results are based on the T $\sim 10^4$ K photoionised gas phase traced by MgII; additional accreting/outflowing material in other gas phases may also be present, but remains undetected in this study. Quasar sightlines consistently show redshifted inflow components and blueshifted outflow components, demonstrating that ultra-strong MgII absorbers trace baryon cycling out to impact parameters of $D = 15$-31 kpc. Moreover, the unexpectedly high prevalence of inflows suggests that ultra-strong MgII absorbers offer a powerful strategy for future surveys to systematically map inflow and outflow cycles across cosmic time.

astro-ph.GA↗

arXiv2025

Connecting Environment, Star Formation History, and Morphology of Massive Quiescent Galaxies at $3<z<4$ with JWST

We present the morphological properties of 17 spectroscopically confirmed massive quiescent galaxies ($10.2 < \log(M_{\ast}/M_{\odot}) < 11.2$) at $3.0 < z < 4.3$, observed with JWST/NIRSpec and NIRCam. Using Sérsic profile fits to F277W and F444W imaging, we derive the size-mass relation and find typical sizes of $\sim$0.6--0.8 kpc at $M_{\ast} = 5 \times 10^{10}~M_{\odot}$, consistent with $\sim$7$\times$ growth from $z \sim 4$ to the present, including $\sim$2$\times$ by $z \sim 2$. We find tentative evidence that formation history and morphology jointly influence galaxy sizes: late-forming bulge-dominated galaxies appear more compact by $\sim$0.2-0.3 dex relative to the expected relation, while late-forming disk-dominated galaxies are larger. Using a random forest regressor, we identify local environmental density, quantified by $\log(1+δ^{\prime}_{3})$ from the three nearest neighbors, as the strongest predictor of bulge-to-total ratio ($B/T$), which spans 0.25-1. In the {\sc IllustrisTNG} simulation, the ex-situ stellar mass fraction ($f_{\ast,\mathrm{ex\text{-}situ}}$) -- a proxy for mergers -- is instead the dominant predictor of $B/T$. Galaxies with high $B/T$ in dense environments show bursty star formation and short quenching timescales ($\lesssim0.4$ Gyr), consistent with bulge growth through merger-driven starbursts; in simulations, such systems exhibit elevated ex-situ fractions ($\sim$20-30%). In contrast, some high-$B/T$ galaxies in intermediate-density environments have low ex-situ fractions, suggesting that additional processes -- such as violent disk instabilities -- also contribute. These results point to multiple bulge growth pathways at high redshift, unified by rapid gas accretion, central starbursts, and AGN feedback, as predicted by cosmological simulations.

astro-ph.GA↗

arXiv2025

COS-EDGES: Co-rotation and Kinematic Stratification of the Multi-Phase CGM Around Edge-On Galaxies

We present the first results from the COS-EDGES survey, targeting the kinematic connection between the ISM and multi-phase circumgalactic medium (CGM) in nine isolated, edge-on galaxies at z~0.2, each probed along its major axis by a background quasar at impact parameters of 13-38kpc. Using VLT/UVES and HST/COS quasar spectra, we analyse MgI, MgII, HI, CII, CIII, and OVI absorption relative to galaxy rotation curves from Keck/LRIS and Magellan/MagE spectra. We find that at lower $D/R_{vir}$ ($D/R_{vir}\leq 0.2$), over 80% of absorption in all ions lies on the side of systemic velocity matching disk rotation, and the optical-depth-weighted median velocity ($v_{abs}$) is consistent with the peak rotation speed. At higher $D/R_{vir}$ ($D/R_{vir} > 0.2$), the kinematics diverge by ionisation state: For low ionisation gas, the amount of co-rotating absorption remains >80%, yet $v_{abs}$ drops to 60% of the galaxy rotation speed. For high ionisation gas (OVI), only 60% of the absorption is consistent with co-rotation and $v_{abs}$ drops to 20% of the rotation speed. Furthermore, the velocity widths, corresponding to 50% of the total optical depth ($Δv_{50}$) for low ionisation gas is 1.8 times larger in the inner halo than at larger radii, while for CIII and OVI $Δv_{50}$ remains unchanged with distance. These results suggest a radially dependent CGM kinematic structure: the inner halo hosts cool, dynamically broad gas tightly coupled to disk rotation, whereas beyond 0.2$R_{vir}$, particularly traced by OVI and HI, the CGM shows weaker rotational alignment and lower velocity dispersion. Therefore, low-ionisation gas likely traces extended co-rotating gas, inflows and/or recycled accretion, while high-ionisation gas reflects a mixture of co-rotating, lagging, discrete collisionally ionised structures, indicating a kinematic stratification of the multi-phase CGM. [Abridged]

astro-ph.GA↗

arXiv2025

Baryonic Ecosystem IN Galaxies (BEINGMgII) -- III. Cool gas reservoirs at $0.3 \le z \le 1.6$ in the Dark Energy Survey

We investigate the origin of intervening cool MgII absorption detected in the spectra of background quasars and the nature of associated galaxies across a broad redshift range of $0.3 \le z \le 1.6$. Using nebular [O II] $λλ$3727,3729 emission lines identified in DESI fiber spectra centered on quasar, we detect 377 galaxies at a typical detection rate of $\sim$0.45% at $z \lesssim 1$, which increases with MgII equivalent width ($W_{2796}$). A significant fraction (74%) of these galaxies are associated with strong absorbers with $W_{2796} \ge$ 2Å. These absorbers trace galaxies spanning stellar masses of $\rm 8.4 \le \log(M_{\star}/M_{\odot}) \le 11.6$ and star formation rates (SFRs) of $\rm -1.2 \le log(SFR~[M_{\odot}yr^{-1}]) \le 2.7$, located at projected galactocentric distances of 4-24 kpc. We find the average MgII absorber strength increases from 2.1Å to 2.9Å between redshifts $z \sim$ 0.4 and 1.2, indicating evolution in the cool gas content of galaxy halos. The relatively constant absorber strength with galactocentric distance implies a clumpy structure of cool gas in the circumgalactic medium (CGM). Further, we find a positive correlation between $W_{2796}$ versus $M_\star$, and SFR, suggesting that the distribution of metal-enriched cool gas in the CGM is closely tied to the properties of the host galaxies. The redshift evolution of gas-phase metallicity suggests that strong MgII absorbers trace the general population of star-forming galaxies. The velocity dispersion of the cool gas increases with halo mass, and the wide range of line of sight velocity offset (-389 to 364 $\rm km\ s^{-1}$) between the galaxy systemic velocity and absorbers highlights the dynamical nature of CGM. However, the majority of this gas remains gravitationally bound to the dark matter halos, consistent with a picture of gas recycling via galactic fountains.

astro-ph.GA↗

arXiv2025

Electron temperature relations in low metallicity, diffuse, and extraplanar gas of starburst galaxies

In this work, we test the validity of $T_e$ - $T_e$ relations in resolved (10-200~pc) measurements of four nearby, low-metallicity (7.25 $\leq$ 12+log(O/H) $\leq$ 8.33), low-mass (10$^{6.78}$ $\leq$ M$_*$/M$_\odot$ $\leq$ 10$^{8.7}$), starburst (10$^{-4.5}$ $\leq$ sSFR $\leq$ 10$^{-0.3}$) galaxies. We obtain VLT/X-Shooter spectra of NGC~5253, NGC~0625, SBS~0335-052E and IC~2828, targeting regions within these galaxies with bright point-like sources and diffuse gas. Our observations are designed to extend from the galaxy midplane into extraplanar gas likely belonging to galactic winds. We measure electron temperatures from five different auroral lines: [NII]~$λ$5755, [OII]~$λλ$7319,30, [SII]~$λλ$4069,76, [SIII]~$λ$6312, and [OIII]~$λ$4363. We compare the resulting $T_e$ - $T_e$ relations with previous studies of HII regions in nearby spiral galaxies. Our results show that $T_e$ - $T_e$ relations in low-metallicity starburst galaxies do not significantly deviate from $T_e$ - $T_e$ relations in HII regions of local spiral galaxies. We do not find significant differences in the diffuse, extraplanar gas. These results suggest that auroral lines provide a reliable metallicity diagnostic not only for high-redshift galaxies but also for the extended diffuse gas in extreme environments like outflows.

astro-ph.GA↗

arXiv2025

Cosmography with the Double Source Plane Strong Gravitational Lens AGEL150745+052256

Strong gravitational lenses with two background sources at widely separated redshifts are a powerful and independent probe of cosmological parameters. We can use these systems, known as Double-Source-Plane Lenses (DSPLs), to measure the ratio ($β$) of angular-diameter distances of the sources, which is sensitive to the matter density ($Ω_m$) and the equation-of-state parameter for dark-energy ($w$). However, DSPLs are rare and require high-resolution imaging and spectroscopy for detection, lens modeling, and measuring $β$. Here we report only the second DSPL ever used to measure cosmological parameters. We model the DSPL AGEL150745+052256 from the ASTRO 3D Galaxy Evolution with Lenses (AGEL) survey using HST/WFC3 imaging and Keck/KCWI spectroscopy. The spectroscopic redshifts for the deflector and two sources in AGEL1507 are $z_{\rm defl}=0.594$, $z_{\rm S1}=2.163$, and $z_{\rm S2}=2.591$. We measure a stellar velocity dispersion of $σ_{\rm obs}=109 \pm 27$ km s$^{-1}$ for the nearer source. Using $σ_{\rm obs}$ for the main deflector (from literature) and S1, we test the robustness of our DSPL model. We measure $β=0.953^{+0.008}_{-0.010}$ for AGEL1507 and infer $Ω_{\rm m}=0.33^{+0.38}_{-0.23}$ for $Λ$CDM cosmology. Combining AGEL1507 with the published model of the Jackpot lens improves the precision on $Ω_{\rm m}$ ($Λ$CDM) and w (wCDM) by $\sim 10 \%$. The inclusion of DSPLs significantly improves the constraints when combined with Plancks cosmic microwave background observations, enhancing precision on w by $30 \%$. This paper demonstrates the constraining power of DSPLs and their complementarity to other standard cosmological probes. Tighter future constraints from larger DSPL samples discovered from ongoing and forthcoming large-area sky surveys would provide insights into the nature of dark energy.

astro-ph.CO↗

arXiv2025

The AGEL Survey Data Release 2: A Gravitational Lens Sample for Galaxy Evolution and Cosmology

The ASTRO 3D Galaxy Evolution with Lenses (AGEL) Survey is an ongoing effort to spectroscopically confirm a diverse sample of gravitational lenses with high spatial resolution imaging, to facilitate a broad range of science outcomes. The AGEL systems span single galaxy-scale deflectors to groups and clusters, and include rare targets such as galaxy-scale lenses with multiple sources, lensed quiescent galaxies, and Einstein rings. We build on the 77 systems presented in Tran et al. 2022 (AGEL data release 1) to present a total 138 lenses, and high resolution F140W and F200LP Hubble Space Telescope images for 71 lenses from a completed HST SNAP program. Lens candidates were originally identified by convolutional neural networks in the DES and DECaLS imaging fields, and of the targets with follow-up spectroscopy we find a high (96%) success rate. Compared with other spectroscopic lens samples, AGEL lenses tend to have both higher redshift deflectors and sources. We briefly discuss the common causes of false-positive candidates, and strategies for mitigating false-positives in next generation lens searches. Lastly, we present 6 galaxy-scale double-source plane lenses useful for cosmological analyses. With next-generation telescopes and surveys such as Euclid, Vera Rubin's Legacy Survey of Space and Time, Keck Observatory's KAPA program, and 4MOST's 4SLSLS surveys on the horizon, the AGEL survey represents a pathfinder for refining automated candidate search methods and identifying and triaging candidates for followup based on scientific potential.

astro-ph.GA↗