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Strong gravitational lenses with two background sources at widely separated redshifts are a promising 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 measuringβ. Here, we report only the second DSPL ever used to measure cosmological parameters. We model the DSPLAGEL150745+052256 from the ASTRO 3D Galaxy Evolution with Lenses (AGEL) survey using Hubble Space Telescope/Wide-Field Camera 3 imaging and Keck Cosmic Web Imager spectroscopy. The spectroscopic redshifts for the deflector and two sources inAGEL1507 arez_defl= 0.594,z_S1 =  2.163, andz_S2= 2.591. We measure a stellar velocity dispersion ofσ_obs = 109 ± 27 km s⁻¹for the nearer source (S1). Usingσ_obsfor the main deflector (from literature) and S1, we test the robustness of our DSPL model. We measure $\beta =0.953_{-0.010}^{+0.008}$forAGEL1507 and infer Ω_m $=0.33_{-0.23}^{+0.38}$for ΛCDM cosmology. CombiningAGEL1507 with the published model of the Jackpot lens improves the precision on Ω_m(ΛCDM) andw(wCDM) by ∼10%. The inclusion of DSPLs significantly improves the constraints when combined with Planck’s cosmic microwave background observations, enhancing the precision onwby 30%. This paper demonstrates the potential 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. 

Abstract Integral field spectroscopy (IFS) is a powerful tool for understanding the formation of galaxies across cosmic history. We present the observing strategy and first results of MSA-3D, a novel JWST program using multi-object spectroscopy in a slit-stepping strategy to produce IFS data cubes. The program observed 43 normal star-forming galaxies at redshifts 0.5 ≲z≲ 1.5, corresponding to the epoch when spiral thin-disk galaxies of the modern Hubble sequence are thought to emerge, obtaining kiloparsec-scale maps of rest-frame optical nebular emission lines with spectral resolutionR≃ 2700. Here we describe the multiplexed slit-stepping method, which is >15 times more efficient than the NIRSpec IFS mode for our program. As an example of the data quality, we present a case study of an individual galaxy atz= 1.104 (stellar massM_*= 10^10.3M_⊙, star formation rate, SFR = 3M_⊙yr⁻¹) with prominent face-on spiral structure. We show that the galaxy exhibits a rotationally supported disk with moderate velocity dispersion ( $\sigma =36_{-4}^{+5}$km s⁻¹), a negative radial metallicity gradient (−0.020 ± 0.002 dex kpc⁻¹), a dust attenuation gradient, and an exponentially decreasing SFR density profile that closely matches the stellar continuum. These properties are characteristic of local spirals, indicating that mature galaxies are in place atz∼ 1. We also describe the customized data reduction and original cube-building software pipelines that we have developed to exploit the powerful slit-stepping technique. Our results demonstrate the ability of JWST slit-stepping to study galaxy populations at intermediate to high redshifts, with data quality similar to current surveys of thez∼ 0.1 Universe. 

Abstract The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from theMSA-3Dsurvey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST’s diffraction limit and a high spectral resolution ofR ≃ 2700. The metallicity gradients measured in our galaxy sample range from −0.03 to 0.02 dex kpc⁻¹. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient atz ∼ 1 with small intrinsic scatter of 0.02 dex kpc⁻¹. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more “disky.” This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution. 

While quiescent galaxies have comparable amounts of cool gas in their outer circumgalactic medium (CGM) compared to star-forming galaxies, they have significantly less interstellar gas. However, open questions remain on the processes causing galaxies to stop forming stars and stay quiescent. Theories suggest dynamical interactions with the hot corona prevent cool gas from reaching the galaxy, therefore predicting the inner regions of quiescent galaxy CGMs are devoid of cool gas. However, there is a lack of understanding of the inner regions of CGMs due to the lack of spatial information in quasar-sightline methods. We present integral-field spectroscopy probing 10–20 kpc (2.4–4.8 Re) around a massive quiescent galaxy using a gravitationally lensed star-forming galaxy. We detect absorption from Magnesium (MgII) implying large amounts of cool atomic gas (108.4–109.3 M⊙ with T~104 Kelvin), in comparable amounts to star-forming galaxies. Lens modeling of Hubble imaging also reveals a diffuse asymmetric component of significant mass consistent with the spatial extent of the MgII absorption, and offset from the galaxy light profile. This study demonstrates the power of galaxy-scale gravitational lenses to not only probe the gas around galaxies, but to also independently probe the mass of the CGM due to it's gravitational effect. 

Abstract The measured ages of massive, quiescent galaxies atz∼ 3–4 imply that massive galaxies quench as early asz∼ 6. While the number of spectroscopic confirmations of quiescent galaxies atz< 3 has increased over the years, there are only a handful atz> 3.5. We report spectroscopic redshifts of one secure (z= 3.757) and two tentative (z= 3.336 andz= 4.673) massive ( $\log \left(M_{*}/M_{\odot }\right)>10.3$) quiescent galaxies with 11 hr of Keck/MOSFIREK-band observations. Our candidates were selected from the FLAMINGOS-2 Extragalactic Near-InfraredK-band Split (FENIKS) survey, which uses deep Gemini/Flamingos-2K_bK_rimaging optimized for increased sensitivity to the characteristic red colors of galaxies atz> 3 with a strong Balmer/4000 Å break. The rest-frameUVJand (ugi)_scolors of three out of four quiescent candidates are consistent with 1–2 Gyr old stellar populations. This places these galaxies as the oldest objects at these redshifts, and challenges the notion that quiescent galaxies atz> 3 are all recently quenched, post-starburst galaxies. Our spectroscopy shows that the other quiescent-galaxy candidate is a broad-line active galactic nucleus (z= 3.594) with strong, redshifted Hβ+ [OIII] emission with a velocity offset > 1000 km s⁻¹, indicative of a powerful outflow. The star formation history of our highest redshift candidate suggests that its progenitor was already in place byz∼ 7–11, reaching ∼10¹¹M_⊙byz≃ 8. These observations reveal the limit of what is possible with deep near-infrared photometry and targeted spectroscopy from the ground and demonstrate that secure spectroscopic confirmation of quiescent galaxies atz> 4 is feasible only with JWST. 

Abstract Deep Very Large Telescope/MUSE optical integral field spectroscopy has recently revealed an abundant population of ultra-faint galaxies (M_UV≈ −15; 0.01L_⋆) atz= 2.9−6.7 due to their strong Lyαemission with no detectable continuum. The implied Lyαequivalent widths can be in excess of 100–200 Å, challenging existing models of normal star formation and indicating extremely young ages, small stellar masses, and a very low amount of metal enrichment. We use JWST/NIRSpec’s microshutter array to follow up 45 of these galaxies (11 hr in G235M/F170LP and 7 hr in G395M/F290LP), as well as 45 lower-equivalent width Lyαemitters. Our spectroscopy covers the range 1.7−5.1 micron in order to target strong optical emission lines: Hα, [Oiii], Hβ, and [N II]. Individual measurements as well as stacks reveal line ratios consistent with a metal-poor nature (2%−40%Z_⊙, depending on the calibration). The galaxies with the highest equivalent widths of Lyα, in excess of 90 Å, have lower [N II]/Hα(1.9σ) and [Oiii]/Hβ(2.2σ) ratios than those with lower equivalent widths, implying lower gas-phase metallicities at a combined significance of 2.4σ. This implies a selection based on Lyαequivalent width is an efficient technique for identifying younger, less chemically enriched systems. 

Abstract We present spectroscopic confirmation of candidate strong gravitational lenses using the Keck Observatory and Very Large Telescope as part of our ASTRO 3D Galaxy Evolution with Lenses ( AGEL ) survey. We confirm that (1) search methods using convolutional neural networks (CNNs) with visual inspection successfully identify strong gravitational lenses and (2) the lenses are at higher redshifts relative to existing surveys due to the combination of deeper and higher-resolution imaging from DECam and spectroscopy spanning optical to near-infrared wavelengths. We measure 104 redshifts in 77 systems selected from a catalog in the DES and DECaLS imaging fields ( r ≤ 22 mag). Combining our results with published redshifts, we present redshifts for 68 lenses and establish that CNN-based searches are highly effective for use in future imaging surveys with a success rate of at least 88% (defined as 68/77). We report 53 strong lenses with spectroscopic redshifts for both the deflector and source ( z src > z defl ), and 15 lenses with a spectroscopic redshift for either the deflector ( z defl > 0.21) or source ( z src ≥ 1.34). For the 68 lenses, the deflectors and sources have average redshifts and standard deviations of 0.58 ± 0.14 and 1.92 ± 0.59 respectively, and corresponding redshift ranges of z defl = 0.21–0.89 and z src = 0.88–3.55. The AGEL systems include 41 deflectors at z defl ≥ 0.5 that are ideal for follow-up studies to track how mass density profiles evolve with redshift. Our goal with AGEL is to spectroscopically confirm ∼100 strong gravitational lenses that can be observed from both hemispheres throughout the year. The AGEL survey is a resource for refining automated all-sky searches and addressing a range of questions in astrophysics and cosmology. 

Abstract Gravitational lenses can magnify distant galaxies, allowing us to discover and characterize the stellar populations of intrinsically faint, quiescent galaxies that are otherwise extremely difficult to directly observe at high redshift from ground-based telescopes. Here, we present the spectral analysis of two lensed, quiescent galaxies atz≳ 1 discovered by theASTRO 3D Galaxy Evolution with Lensessurvey:AGEL1323 (M_*∼ 10^11.1M_⊙,z= 1.016,μ∼ 14.6) andAGEL0014 (M_*∼ 10^11.5M_⊙,z= 1.374,μ∼ 4.3). We measured the age, [Fe/H], and [Mg/Fe] of the two lensed galaxies using deep, rest-frame-optical spectra (S/N ≳40 Å⁻¹) obtained on the Keck I telescope. The ages ofAGEL1323 andAGEL0014 are ${5.6}_{-0.8}^{+0.8}$Gyr and ${3.1}_{-0.3}^{+0.8}$Gyr, respectively, indicating that most of the stars in the galaxies were formed less than 2 Gyr after the Big Bang. Compared to nearby quiescent galaxies of similar masses, the lensed galaxies have lower [Fe/H] and [Mg/H]. Surprisingly, the two galaxies have comparable [Mg/Fe] to similar-mass galaxies at lower redshifts, despite their old ages. Using a simple analytic chemical evolution model connecting the instantaneously recycled element Mg with the mass-loading factors of outflows averaged over the entire star formation history, we found that the lensed galaxies may have experienced enhanced outflows during their star formation compared to lower-redshift galaxies, which may explain why they quenched early. 

Abstract The James Webb Space Telescope is revealing a new population of dust-reddened broad-line active galactic nuclei (AGN) at redshiftsz≳ 5. Here we present deep NIRSpec/Prism spectroscopy from the Cycle 1 Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) of 15 AGN candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the UV. From NIRCam photometry alone, they could have been dominated by dusty star formation or an AGN. Here we show that the majority of the compact red sources in UNCOVER are dust-reddened AGN: 60% show definitive evidence for broad-line Hαwith a FWHM > 2000 km s⁻¹, 20% of the current data are inconclusive, and 20% are brown dwarf stars. We propose an updated photometric criterion to select redz> 5 AGN that excludes brown dwarfs and is expected to yield >80% AGN. Remarkably, among allz_phot> 5 galaxies with F277W – F444W > 1 in UNCOVER at least 33% are AGN regardless of compactness, climbing to at least 80% AGN for sources with F277W – F444W > 1.6. The confirmed AGN have black hole masses of 10⁷–10⁹M_⊙. While their UV luminosities (−16 >M_UV> −20 AB mag) are low compared to UV-selected AGN at these epochs, consistent with percent-level scattered AGN light or low levels of unobscured star formation, the inferred bolometric luminosities are typical of 10⁷–10⁹M_⊙black holes radiating at ∼10%–40% the Eddington limit. The number densities are surprisingly high at ∼10⁻⁵Mpc⁻³mag⁻¹, 100 times more common than the faintest UV-selected quasars, while accounting for ∼1% of the UV-selected galaxies. While their UV faintness suggests they may not contribute strongly to reionization, their ubiquity poses challenges to models of black hole growth.