arXiv subjects

Karl Glazebrook

Publications and source records attributed to Karl Glazebrook.

At least 55 records · Page 3Linked to original sources

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.

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arXiv2026

The MAGPI Survey: co-evolution of baryons and dark matter in star-forming disk-like galaxies at $0.1 \lesssim z \lesssim 0.85$

We present a comprehensive analysis of the dark matter (DM) content and its structural dependence in star-forming disk-like galaxies at intermediate redshifts ($0.1 \lesssim z \lesssim 0.85$), utilizing spatially resolved kinematic data from the MAGPI survey. We report the following: (1) Low stellar mass galaxies ($M_{\rm star} < 10^{9.5}\, M_\odot$) are strongly DM dominated across all radii, with average $\langle f_{_{\rm DM}} \rangle \sim 0.85$, while high-mass ($M_{\rm star} > 10^{10.5}\, M_\odot$) systems exhibit relatively low DM fractions in their inner regions ($\langle f_{_{\rm DM}} \rangle \sim 0.47$) which is equivalent to local massive disk galaxies (e.g., Milky Way and Andromeda). This suggests a mass-dependent structural dichotomy, most-likely governed by a combination of internal galactic processes and environmental influences. (2) A tight inverse correlation between $f_{_{\rm DM}}$ and baryon mass surface density ($Σ_{\rm bar}$), with intrinsic scatter of $\sim 0.11$ dex. This is consistent with an inside-out baryon assembly scenario and suggests that the fundamental structural correlations of galaxies were already established by $z\sim 0.85$. (3) No significant evolution in $f_{_{\rm DM}}$ with redshift across the MAGPI window, and when combined with higher-redshift ($0.6 \leq z \leq 1.5$) data from Sharma et al. 2025, we quantitatively show that the reported decline in $f_{_{\rm DM}}(z)$ is most-likely due to observational biases against low-mass systems at $z > 1$. These results offer empirical evidence for a scenario in which disk-like galaxies evolve through a co-regulated build-up of baryonic and DM components, preserving internal structural regularities (such as the total mass distribution and rotation-curve shape) throughout cosmic time.

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arXiv2026

A Portrait of the Cosmic Reionisation History in the Context of the Early Dark Energy Model

Recent JWST observations of Lyman-$α$ emission at $z \sim 11-6$ indicate a rapid reionization of the intergalactic medium within the first $\sim700$ Myr. The required Lyman continuum (LyC) photon budget may naturally arise from the unexpectedly high galaxy number densities revealed by JWST, reducing the need for scenarios invoking very high LyC escape fractions ($f_{\rm esc}\gtrsim0.2$) or dominant contributions from ultra-faint galaxies ($M_{\rm UV}>-15$) in the standard $Λ$CDM framework. In this work, we model the reionization history under the Early Dark Energy (EDE) paradigm -- originally proposed to ease the Hubble tension -- which also explains the observed over-abundance of high-$z$ galaxies without extreme star formation efficiencies. The EDE model yields reionization histories consistent with current constraints while requiring only moderate LyC escape fractions and UV luminosity densities ($f_{\rm esc}\sim 0.05-0.1$, $M_{\rm UV}\lesssim -17$ to $-15$). Our results suggest that, once key astrophysical parameters are better constrained, the reionization history could serve as an independent and complementary probe of EDE cosmologies.

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arXiv2025

The AURORA Survey: The Mass -- Metallicity and Fundamental Metallicity Relations at $z \sim 2.3$ Based Purely on Direct $T_e$ Metallicities

We present new constraints on the Mass -- Metallicity (MZR) and Fundamental Metallicity Relations (FMR) using a sample of 34 galaxies at $1.38\leq~z\leq~3.5$ (median $z=2.28$). These galaxies have direct $T_e$ measurements from [O\sc{iii}]4363Å~and/or [O\sc{ii}]7320,7331Å~auroral emission lines detected with \textit{JWST}/NIRSpec as part of the AURORA survey. The detection of both oxygen auroral lines allows for dual-zone direct $T_e$ measurements and expands the dynamic range in $12+\log\mathrm{(O/H)}$ (7.68 to 8.65 dex), stellar mass ($10^{8}$ to $10^{10.4}$ M$_\odot$), and star-formation rate ($1$ to $100$ M$_\odot$ yr$^{-1}$) compared to previous direct $T_e$ studies of the high-redshift MZR and FMR. We characterize the $z\sim2$ MZR and find a slope of $0.27\pm0.04$ and normalization of $12+\log\mathrm{(O/H)} = 8.44\pm0.04$ at $10^{10}$ M$_\odot$ with an intrinsic scatter of 0.10 dex, consistent with past strong-line MZR measurements. Comparisons with $z\sim2$ predictions from six simulations reveal that none reproduce our observed MZR normalization evolution between $z\sim0$ and $z\sim2$. This discrepancy suggests current models do not fully capture the chemical enrichment and feedback processes occurring at cosmic noon. However, all 34 galaxies are on or above the star-forming main sequence such that our sample may be biased towards lower $12+\log\mathrm{(O/H)}$ if the FMR persists at $z\sim2$. Correcting for this selection effect would increase O/H by $\approx0.1$ dex at 10$^{9.3}$ M$_\odot$ (the median mass of our sample) bringing our MZR into better agreement with that of \texttt{TNG}. Lastly, we find our $z\sim2.3$ sample is consistent with the $z\sim0$ FMR within 0.1 dex in O/H, indicating that the smooth secular mechanisms regulating chemical enrichment, star formation, stellar mass, and outflows were in place at cosmic noon.

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arXiv2025

KURVS: chemical properties from multiple strong line calibrations for star-forming galaxies at $z\sim1.5$

Gas-phase oxygen abundance (metallicity) properties can be constrained through emission line analyses, and are of great importance to investigate galaxy evolution histories. We present an analysis of the integrated and spatially-resolved rest-frame optical emission line properties of the ionised gas in 43 star-forming galaxies at $z\sim1.5$ in the KMOS Ultra-deep Rotational Velocity Survey (KURVS). Using the [NII]$\lambda6584$/H$α$ (N$_2$), ([OII]$λ\lambda3727,9+$[OIII]$λ\lambda4959,5007$)/H$β$ (R23), and for the first time [NII]$\lambda6584$/[OII]$λ\lambda3727,9$ (N$_2$O$_2$) indicators at this redshift, we measure the gas-phase metallicities and their radial gradients. On $\sim4$-kpc scales metallicity gradients measured from N$_2$O$_2$ and those measured from N$_2$ are in good agreement when considering the spatial distributions of dust in each galaxy, as parameterised by dust attenuation radial gradients. We report a nearly flat metallicity gradient distribution typically at $z\sim1.5$, with the 50th, 16th and 84th percentiles at $0.01$, $-0.03$, and $0.05$ dex kpc$^{-1}$, respectively. The findings agree well with previous observational studies and simulations at this epoch. We ascribe the observed negative metallicity gradients to a natural result from self-regulating systems, and the positive ones to potential galactic fountains and higher merger rates.

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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.

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arXiv2025

Where Galaxies Go to Die: The Environments of Massive Quiescent Galaxies at $3<z<5$

At low redshift, massive quiescent galaxies (MQGs) are most frequently found in massive, rich galaxy clusters, but at high redshift the trend is less clear. Here, we present spectroscopic evidence of the effects of environment on the formation and assembly of high-redshift MQGs. We identify 25 (5) $\log (M_*/\mathrm{M_\odot}\geq10.5$ ($10.0\leq\log (M_*/\mathrm{M_\odot}<10.5$) spectroscopically-confirmed quiescent galaxies in the UDS and EGS fields at $3 5$, finding that the masses from the inferred MQG SFHs regularly exceed either observed or simulated high-redshift galaxies, which suggests indicates that mergers and ex-situ star formation play a key role in the mass assembly of MQGs in overdense environments.

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arXiv2025

The Dual Nature of GHZ9: Coexisting Active Galactic Nuclei and Star Formation Activity in a Remote X-ray Source at z = 10.145

We present James Webb Space Telescope (JWST)/NIRSpec PRISM spectroscopic characterization of GHZ9 at z= 10.145 $\pm$ 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including CII, SiIV, NIV], CIV, HeII, OIII], NIII], and CIII]. The prominent rest-frame equivalent widths (EW(CIV)$\simeq$65A, EW(OIII])$\simeq$28A, EW(CIII])$\simeq$48A) show the presence of a hard active galactic nucleus (AGN) radiation field, while line ratio diagnostics are consistent with either AGN or star formation as the dominant ionizing source. GHZ9 is nitrogen-enriched (6--9.5 (N/O)$_{\odot}$), carbon-poor (0.2--0.65 (C/O)$_{\odot}$), metal-poor (Z = 0.01--0.1 Z$_{\odot}$), and compact ($<$ 106 pc), similarly to GN-z11, GHZ2, and recently discovered N-enhanced high redshift objects. We exploited the newly available JWST/NIRSpec and NIRCam data set to perform an independent analysis of the Chandra data confirming that GHZ9 is the most likely JWST source associated with X-ray emission at 0.5-7 keV. Assuming a spectral index $Γ$ = 2.3 (1.8), we estimate a black hole (BH) mass of 1.60 $\pm$ 0.31 (0.48 $\pm$ 0.09) $\times$ 10$^8$M$_{\odot}$, which is consistent either with Eddington-accretion onto heavy ($\geq$ 10$^6$ M$_{\odot}$) BH seeds formed at z=18, or super-Eddington accretion onto a light seed of $\sim$ 10$^2-10^4$ M$_{\odot}$ at z = 25. The corresponding BH-to-stellar mass ratio M$_{BH}$/M$_{star}$= 0.33$\pm$0.22 (0.10$\pm$0.07), with a stringent limit $>$0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN-galaxy coevolution with future multi-frequency observations.

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arXiv2025

MSA-3D: Uncovering Weak AGNs and Resolved Outflows in Disguise in $z\sim1$ Star-Forming Galaxies

We present spatially resolved rest-optical spectroscopy of 38 star-forming galaxies at 0.5 < z < 1.7 from the JWST/NIRSpec MSA-3D survey, which uses slit-stepping to build IFU-like datacubes at 0.1'' resolution. We map emission-line morphology, excitation, and kinematics of the warm ionized gas using [N II]/H$α$, [S II]/H$α$, and [O III]/H$β$. Relative to z$\sim$0 galaxies at fixed stellar mass, our sources show systematically lower [N II]/H$α$ and [S II]/H$α$ and elevated [O III]/H$β$, consistent with harder radiation fields and lower metallicities. Radially, [O III]/H$β$ profiles are typically flat or mildly positive, whereas [N II]/H$α$ also remains flat or declines outward, mirroring metallicity trends. On kpc scales, we find a strong positive correlation between [N II]/H$α$ and velocity dispersion ($σ$), linking local excitation to turbulent or shock-driven kinematics. Six galaxies ($\sim$ 16% of the sample) host spatially localized regions with elevated [N II]/H$α$, high EW(H$α$), and V_RMS = $\sqrt{V^2 + σ^2} > 200$ km/s, indicative of weak AGN activity, shocks, or outflows. For these candidates we infer modest warm-ionized outflow rates of 1-4 Msun/yr and kinetic powers $\sim$ 0.1-1% of the AGN bolometric luminosity (from central [O III] or H$α$). These values place our sample at the low-energy tail of known AGN-driven outflows yet in continuity with $\dot{M_{out}}-L_{AGN}$ scaling relations across 0 < z < 6. A completeness assessment shows MSA-3D is sensitive to AGN with $L_{AGN} \geq 10^{43}$ erg/s, underscoring both the promise and current limitations of detecting weak AGN activity in distant galaxies with resolved spectroscopy.

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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.

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arXiv2025

What you see is what you get: empirically measured bolometric luminosities of Little Red Dots

New populations of red active galactic nuclei (known as ``Little Red Dots'') discovered by JWST exhibit remarkable spectral energy distributions. Leveraging X-ray through far-infrared observations of two of the most luminous known Little Red Dots, we directly their bolometric luminosities. We find evidence that more than half of the bolometric luminosity likely emerges in the rest-frame optical, with $L_{\rm bol}/L_{5100} = 5$, roughly half the value for ``standard'' Active Galactic Nuclei. Meanwhile, the X-ray emitting corona, UV-emitting black-body, and reprocessed mid to far-infrared emission are all considerably sub-dominant, assuming that the far-infrared luminosity is well below current measured limits. We present new bolometric corrections that dramatically lower inferred bolometric luminosities by a factor of ten compared to published values in the literature. These bolometric corrections are in accord with expectations from models in which gas absorption and reprocessing are responsible for the red rest-frame optical colors of Little Red Dots. We discuss how this lowered luminosity scale suggests a lower mass scale for the population by at least an order of magnitude {\bf (e.g., $\sim 10^5-10^7~{\rm M_{\odot}}$ black holes, and $\sim 10^8~{\rm M_{\odot}}$ galaxies)}, alleviating tensions with clustering, overmassive black holes, and the integrated black hole mass density in the Universe.

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arXiv2025

UNCOVER/MegaScience: No Evidence of Environmental Quenching in a z$\sim$2.6 Proto-cluster

Environmental quenching -- where interactions with other galaxies and/or the intra-cluster medium (ICM) suppress star formation in low-mass galaxies -- has been well-established as the primary driver behind the formation of the red sequence for low-mass galaxies within clusters at low redshift ($z<1$). However, it remains unclear whether these mechanisms are active at higher-redshifts in proto-cluster environments that are not yet fully virialized. In large part, this regime has remained unexplored due to observational limitations; however, JWST has recently opened a new window into the role of environmental quenching on low-mass (log(M$_{\star}$/M$_{\odot}$$<$9.0) galaxies at cosmic noon ($2 < z < 3$). Here, we leverage the deep imaging and R$\sim$15 spectrophotometry enabled by the 20 band JWST/NIRCam data from the UNCOVER and MegaScience programs to examine environmental quenching in a newly discovered $z\approx2.58$ proto-cluster. We compare the star formation histories (SFHs) of 19 low-mass quiescent galaxies in the proto-cluster to a matched sample of 18 in the field, and find no significant differences. This similarity extends to galaxy sizes and quenched fractions, which also show no significant differences between the two environments across the full stellar mass range (8.5$<$log(M$_{\star}$/M$_{\odot}$$\leq$11.0). This indicates that the proto-cluster has not yet accelerated quenching relative to the field and is consistent with expectations that $z>2$ proto-clusters have yet to virialize and develop a dense enough environment required to efficiently quench low-mass galaxies.

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arXiv2025

The Structure and Formation Histories of Low-Mass Quiescent Galaxies in the Abell 2744 Cluster Environment

Low-mass quiescent galaxies are thought to predominantly reside in overdense regions, as environmental effects are often invoked to explain their shutdown of star formation. These longer-timescale quenching mechanisms - such as interactions with hot gas in the intracluster medium and dynamical encounters with other cluster galaxies - leave imprints on galaxy morphologies, emphasizing the importance of quantifying the structures of low-mass quiescent galaxies in galaxy clusters at $z<0.5$. Using spectrophotometric data from the UNCOVER and MegaScience programs, we present the first measurement of the quiescent size-mass relation between $7<\log(M_\star/M_\odot)<10$ using JWST imaging, based on a sample of 1531 galaxies in the $z=0.308$ Abell 2744 galaxy cluster. The resulting size-mass relation has a significantly higher scatter than similar-redshift field samples, despite comparable best-fit relations in both the dwarf and intermediate-mass regimes. Both "progenitor bias", where larger, diskier low-mass galaxies enter the cluster at later epochs, and a general expansion of galaxy structure from dynamical interactions could be at play. This evolutionary framework is further supported by the tentative evidence that older low-mass quiescent galaxies in the cluster are more spheroidal. The star-formation histories derived for our cluster sample imply their formation and quenching occurs relatively late, at $z<1.5$. In this scenario, the progenitor population would have disky axis-ratio distributions at cosmic noon, in agreement with recent observations. While this leaves ample time for dynamical interactions to maintain quiescence and drive the observed subsequent morphological evolution post-quenching, the data disfavors an onset of quenching due to the environment.

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arXiv2025

Resolved Stellar and Nebular Kinematics of a Star-forming Galaxy at $z\sim2$

The kinematics of star-forming galaxy populations at high redshifts are integral to our understanding of disk properties, merger rates, and other defining characteristics. Nebular gas emission is a common tracer of galaxies' gravitational potentials and angular momenta, but is sensitive to non-gravitational forces as well as galactic outflows, and thus might not accurately trace the host galaxy dynamics. We present kinematic maps of young stars from rest-ultraviolet photospheric absorption in the star-forming galaxy CASSOWARY 13 (a.k.a. SDSS J1237+5533) at $z=1.87$ using the Keck Cosmic Web Imager, alongside nebular emission measurements from the same observations. Gravitational lensing magnification of the galaxy enables good spatial sampling of multiple independent lensed images. We find close agreement between the stellar and nebular velocity fields. We measure a mean local velocity dispersion of $σ= 64\pm12$ km$\,$s$^{-1}$ for the young stars, consistent with that of the H II regions traced by nebular C III] emission ($52\pm9$ km$\,$s$^{-1}$). The $\sim20$ km$\,$s$^{-1}$ average difference in line-of-sight velocity is much smaller than the local velocity width and the velocity gradient ($\gtrsim 100$ km$\,$s$^{-1}$). We find no evidence of asymmetric drift nor evidence that outflows bias the nebular kinematics, and thus conclude that nebular emission appears to be a reasonable dynamical tracer of young stars in the galaxy. These results support the picture of star formation in thick disks with high velocity dispersion at $z\sim2$, and represent an important step towards establishing robust kinematics of early galaxies using collisionless tracers.

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arXiv2025

A fast radio burst from the first 3 billion years of the Universe

Fast radio bursts (FRBs) are enigmatic millisecond-duration signals which encode otherwise unattainable information on the plasma which permeates our Universe, providing insights into magnetic fields and gas distributions. Here we report the discovery of FRB 20240304B originating at redshift 2.148 +/- 0.001 corresponding to just 3 billion years after the Big Bang. FRB 2024030 was detected with the MeerKAT radio telescope and localized to a low-mass, clumpy, star forming galaxy using the James Webb Space Telescope. This discovery doubles the redshift reach of localized FRBs and probes ionized baryons across ~80% of cosmic history. Its sightline, intersecting the Virgo Cluster and a foreground group, reveals magnetic field complexity over many gigaparsec scales. Our observations establish FRB activity during the peak of cosmic star formation and demonstrate that FRBs can probe galaxy formation during the most active era in cosmic time.

astro-ph.HE↗

arXiv2025

MINERVA: A NIRCam Medium Band and MIRI Imaging Survey to Unlock the Hidden Gems of the Distant Universe

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 5$σ$ depth of 28.1 mag in F300M and covers $\sim$ 542 arcmin$^2$, increasing the area of existing JWST medium-band coverage in at least 8 bands by $\sim$ 7$\times$. The MIRI imaging reaches a 5$σ$ depth of 23.9 mag in F1280W and covers $\sim$ 275 arcmin$^2$ 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 $< z <$ 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.

astro-ph.GA↗

arXiv2025

Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1

JWST observations have uncovered a new population of red, compact objects at high redshifts dubbed `Little Red Dots' (LRDs), which typically show broad emission lines and are thought to be dusty Active Galactic Nuclei (AGN). Some of their other features, however, challenge the AGN explanation, such as prominent Balmer breaks and extremely faint or even missing metal high-ionization lines, X-ray, or radio emission, including in deep stacks. Time variability is another, robust, test of AGN activity. Here, we exploit the $z=7.045$ multiply-imaged LRD A2744-QSO1, which offers a particularly unique test of variability due to lensing-induced time delays between the three images spanning 22 yr (2.7 yr in the rest-frame), to investigate its photometric and spectroscopic variability. We find the equivalent widths (EWs) of the broad H$α$ and H$β$ lines, which are independent of magnification and other systematics, to exhibit significant variations, up to $18\pm3$ % for H$α$ and up to $22\pm8$ % in H$β$, on a timescale of 875 d (2.4 yr) in the rest-frame. This suggests that A2744-QSO1 is indeed an AGN. We find no significant photometric variability beyond the limiting systematic uncertainties, so it currently cannot be determined whether the EW variations are due to line-flux or continuum variability. These results are consistent with a typical damped random walk (DRW) variability model for an AGN like A2744-QSO1 ($M_{\mathrm{BH}}=4\times10^7 \mathrm{M}_{\odot}$) given the sparse sampling of the light-curve with the available data. Our results therefore support the AGN interpretation of this LRD, and highlight the need for further photometric and spectroscopic monitoring in order to build a detailed and reliable light-curve.

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↗