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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 R e ) 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 (10 8.4 –10 9.3 M ⊙ with T~10 4 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. Quiescent galaxies have similar amount of cool gas to star forming galaxies, yet why galaxies stop forming stars remains an open question. The authors investigate why passive galaxies remain quiescent using a gravitationally lensed background galaxy to probe the faint, diffuse cool gas around a massive quiescent galaxy, and use lensing configuration to constrain the total mass and geometry of this gas reservoir.

Observed evolution of the total mass distribution with redshift is crucial to testing galaxy evolution theories. To measure the total mass distribution, strong gravitational lenses complement the resolved dynamical observations currently limited to \\(z \\lesssim 0.5\\). Here we present the lens models for a pilot sample of seven galaxy-scale lenses from the ASTRO3D Galaxy Evolution with Lenses (AGEL) survey. The AGEL lenses, modeled using HST/WFC3-F140W images with Gravitational Lens Efficient Explorer (GLEE) software, have deflector redshifts between \\(0.3 < z_{\\rm defl} < 0.9\\). Assuming a power-law density profile with slope \\(\\gamma\\), we measure the total density profile for the deflector galaxies via lens modeling. We also measure the stellar velocity dispersions (\\(\\sigma_{\\rm obs}\\)) for four lenses and obtain \\(\\sigma_{\\rm obs}\\) from SDSS-BOSS for the remaining lenses to test our lens models by comparing observed and model-predicted velocity dispersions. For the seven AGEL lenses, we measure an average density profile slope of \\(-1.95 \\pm 0.09\\) and a \\(\\gamma\\)--\\(z\\) relation that does not evolve with redshift at \\(z<1\\). Although our result is consistent with some observations and simulations, it differs from other studies at \\(z<1\\) that suggest the \\(\\gamma\\)--\\(z\\) relation evolves with redshift. The apparent conflicts among observations and simulations may be due to a combination of 1) systematics in the lensing and dynamical modeling; 2) challenges in comparing observations with simulations; and 3) assuming a simple power-law for the total mass distribution. By providing more lenses at \\(z_{\\rm defl} > 0.5\\), the AGEL survey will provide stronger constraints on whether the mass profiles evolve with redshift as predicted by current theoretical models.

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 13, 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\\(\\alpha\\) emission (including seven new redshifts determined here adding to those presented previously in Sheu et al. (2024)). The lensed sources span a redshift range from z=0.96 to 4.09 with most of them showing 3-5 images, including four sources displaying central or radial images. In total, we identify 43 images of these 13 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 \\(\\Omega_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} \\approx 1.2 \\times 10^{15} M_\\odot\\).

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 R\\textsubscript{e}) 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 (10\\textsuperscript{8.4} -- 10\\textsuperscript{9.3} M\\textsubscript{\\(\\odot\\)} with T\\(\\sim\\)10\\textsuperscript{4} 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.

We study the spatially resolved outflow properties of CSWA13, an intermediate mass (\\(M_*=10^{9}~\\mathrm{M}_{\\odot}\\)), gravitationally lensed star-forming galaxy at \\(z=1.87\\). We use Keck/KCWI to map outflows in multiple rest-frame ultraviolet ISM absorption lines, along with fluorescent Si II\\(^*\\) emission, and nebular emission from C III] tracing the local systemic velocity. The spatial structure of outflow velocity mirrors that of the nebular kinematics, which we interpret to be a signature of a young galactic wind that is pressurizing the ISM of the galaxy but is yet to burst out. From the radial extent of Si II\\(^*\\) emission, we estimate that the outflow is largely encapsulated within \\(3.5\\) kpc. We explore the geometry (e.g., patchiness) of the outflow by measuring the covering fraction at different velocities, finding that the maximum covering fraction is at velocities \\(v\\simeq-150\\) km\\(\\,\\)s\\(^{-1}\\). Using the outflow velocity (\\(v_{out}\\)), radius (\\(R\\)), column density (\\(N\\)), and solid angle (\\(\\Omega\\)) based on the covering fraction, we measure the mass loss rate \\(\\log\\dot{m}_{out}/(\\mathrm{M}_{\\odot}\\text{yr}^{-1}) = 1.73\\pm0.23\\) and mass loading factor \\(\\log\\eta = 0.04\\pm0.34\\) for the low-ionization outflowing gas in this galaxy. These values are relatively large and the bulk of the outflowing gas is moving with speeds less than the escape velocity of the galaxy halo, suggesting that the majority of outflowing mass will remain in the circumgalactic medium and/or recycle back into the galaxy. The results support a picture of high outflow rates transporting mass and metals into the inner circumgalactic medium, providing the gas reservoir for future star formation.

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 at \\(z\\gtrsim 1\\) discovered by the ASTRO 3D Galaxy Evolution with Lenses survey: AGEL1323 (\\(M_*\\sim 10^{11.1}M_{\\odot}\\), \\(z=1.016\\), \\(\\mu \\sim 14.6\\)) and AGEL0014 (\\(M_*\\sim 10^{11.5}M_{\\odot}\\), \\(z=1.374\\), \\(\\mu \\sim 4.3\\)). We measured the age, [Fe/H], and [Mg/Fe] of the two lensed galaxies using deep, rest-frame-optical spectra (S/N \\(\\gtrsim 40\\)~$\\mathring {\\mathrm A}$$^{-1}\\() obtained on the Keck~I telescope. The ages of AGEL1323 and AGEL0014 are \\)5.6^{+0.8}_{-0.8}\\(~Gyr and \\)3.1^{+0.8}_{-0.3}$~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.