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We present a survey undertaken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the galaxies associated with a representative sample of 16 damped Lyα absorbers (DLAs) at z ≈ 4.1–4.5, using the [C ii] 158 μm ([C ii]) line. We detect seven [C ii]-emitting galaxies in the fields of five DLAs, all of which have absorption metallicity [M/H] > −1.5. We find that the detectability of these H i-selected galaxies with ALMA is a strong function of DLA metallicity, with a detection rate of 71−20+11 % for DLAs with [M/H] > −1.5 and 0+18% for DLAs with [M/H] < −1.5. The identified DLA galaxies have far-IR properties similar to those of typical star-forming galaxies at z ∼ 4, with estimated obscured star formation rates ranging from ≲6 M⊙ yr−1 to 110 M⊙ yr−1. High-metallicity DLAs therefore provide an efficient way to identify and study samples of high-redshift, star-forming galaxies, without preselecting the galaxies by their emission properties. The agreement between the velocities of the metal absorption lines of the DLA and the [C ii] emission line of the DLA galaxy indicates that the metals within the DLA originated in the galaxy. With observed impact parameters between 14 and 59 kpc, this indicates that star-forming galaxies at z ∼ 4 have a substantial reservoir of dense, cold, neutral gas within their circumgalactic medium that has been enriched with metals from the galaxy.

We use deep spectroscopy from the Hubble Space Telescope Wide-Field-Camera 3 IR grisms combined with broadband photometry to study the stellar populations, gas ionization and chemical abundances in star-forming galaxies at z ∼ 1.1–2.3. The data stem from the CANDELS Lyα Emission At Reionization (CLEAR) survey. At these redshifts, the grism spectroscopy measure the [O II] λ λ3727, 3729, [O III]λ λ4959, 5008, and Hβ strong emission features, which constrain the ionization parameter and oxygen abundance of the nebular gas. We compare the line-flux measurements to predictions from updated photoionization models (MAPPINGS V; Kewley et al.), which include an updated treatment of nebular gas pressure, logP/k=neTe . Compared to low-redshift samples (z ∼ 0.2) at fixed stellar mass, logM*/M⊙= 9.4–9.8, the CLEAR galaxies at z = 1.35 (1.90) have lower gas-phase metallicity, Δ(logZ) = 0.25 (0.35) dex, and higher ionization parameters, Δ(logq) = 0.25 (0.35) dex, where U ≡ q/c. We provide updated analytic calibrations between the [O III], [O II], and Hβ emission-line ratios, metallicity, and ionization parameter. The CLEAR galaxies show that at fixed stellar mass, the gas ionization parameter is correlated with the galaxy specific star formation rates, where Δlogq≃0.4×Δ(logsSFR) , derived from changes in the strength of galaxy Hβ equivalent width. We interpret this as a consequence of higher gas densities, lower gas covering fractions, combined with a higher escape fraction of H-ionizing photons. We discuss both tests to confirm these assertions and implications this has for future observations of galaxies at higher redshifts.

The metallicity and gas density dependence of interstellar depletions, the dust-to-gas (D/G), and dust-to-metal (D/M) ratios have important implications for how accurately we can trace the chemical enrichment of the universe, either by using FIR dust emission as a tracer of the ISM or by using spectroscopy of damped Lyα systems to measure chemical abundances over a wide range of redshifts. We collect and compare large samples of depletion measurements in the Milky Way (MW), Large Magellanic Cloud (LMC) (Z = 0.5 Z ⊙), and Small Magellanic Cloud (SMC) (Z = 0.2 Z ⊙). The relations between the depletions of different elements do not strongly vary between the three galaxies, implying that abundance ratios should trace depletions accurately down to 20% solar metallicity. From the depletions, we derive D/G and D/M. The D/G increases with density, consistent with the more efficient accretion of gas-phase metals onto dust grains in the denser ISM. For log N(H) > 21 cm−2, the depletion of metallicity tracers (S, Zn) exceeds −0.5 dex, even at 20% solar metallicity. The gas fraction of metals increases from the MW to the LMC (factor 3) and SMC (factor 6), compensating for the reduction in total heavy element abundances and resulting in those three galaxies having the same neutral gas-phase metallicities. The D/G derived from depletions are respective factors of 2 (LMC) and 5 (SMC) higher than the D/G derived from FIR, 21 cm, and CO emission, likely due to the combined uncertainties on the dust FIR opacity and on the depletion of carbon and oxygen.

We present a sample of nine fast radio bursts (FRBs) from which we derive magnetic field strengths of the host galaxies represented by normal, z < 0.5 star-forming galaxies with stellar masses M * ≈ 108–1010.5 M ⊙. We find no correlation between the FRB rotation measure (RM) and redshift, which indicates that the RM values are due mostly to the FRB host contribution. This assertion is further supported by a significant positive correlation (Spearman test probability P S < 0.05) found between the RM and the estimated host dispersion measure (DMhost; with Spearman rank correlation coefficient r S = +0.75). For these nine galaxies, we estimate their magnetic field strengths projected along the sight line ∣B ∥∣, finding a low median value of 0.5 μG. This implies the magnetic fields of our sample of hosts are weaker than those characteristic of the solar neighborhood (≈6 μG), but relatively consistent with a lower limit on the observed range of ≈2–10 μG for star-forming disk galaxies, especially as we consider reversals in the B-field, and that we are only probing B∥. We compare to RMs from simulated galaxies of the Auriga project—magneto-hydrodynamic cosmological zoom simulations—and find that the simulations predict the observed values to within a 95% confidence interval. Upcoming FRB surveys will provide hundreds of new FRBs with high-precision localizations, RMs, and imaging follow-up to support further investigation into the magnetic fields of a diverse population of z < 1 galaxies.

We present Keck Cosmic Web Imager Lyα integral field spectroscopy of the fields surrounding 14 damped Lyα absorbers (DLAs) at z ≈ 2. Of these 14 DLAs, nine have high metallicities ([M/H] > − 0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Lyα line flux sensitivities of ∼2 × 10−17 erg s−1 cm−2 over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Lyα flux of three known Lyα-emitting H i-selected galaxies in our sample. In addition, we find two Lyα emitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA at z ≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Lyα emission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Lyα emitters, we conclude that H i-selected galaxies associated with high-metallicity DLAs at z ≈ 2 are dusty and therefore might feature low Lyα escape fractions. Our results indicate that complementary approaches—using Lyα, CO, Hα, and [C ii] 158 μm emission—are necessary to identify the wide range of galaxy types associated with z ≈ 2 DLAs.

The cycling of metals between interstellar gas and dust is a critical aspect of the baryon cycle of galaxies, yet our understanding of this process is limited. This study focuses on understanding dust depletion effects in the low-metallicity regime (<20% Z ⊙) typical of cosmic noon. Using medium-resolution UV spectroscopy from the Cosmic Origins Spectrograph on board the Hubble Space Telescope, gas-phase abundances and depletions of iron and sulfur were derived toward 18 sight lines in local dwarf galaxies IC 1613 and Sextans A. The results show that the depletion of Fe and S is consistent with that found in the Milky Way (MW), LMC, and SMC. The depletion level of Fe increases with gas column density, indicating dust growth in the interstellar medium. The level of Fe depletion decreases with decreasing metallicity, resulting in the fraction of iron in gas ranging from 3% in the MW to 9% in IC 1613 and ∼19% in Sextans A. The dust-to-gas and dust-to-metal ratios (D/G, D/M) for these dwarf galaxies were estimated based on the MW relations between the depletion of Fe and other elements. The study finds that D/G decreases only slightly sublinearly with metallicity, with D/M decreasing from 0.41 ± 0.05 in the MW to 0.11 ± 0.11 at 0.10 Z ⊙ (at log N(H) = 21 cm−2). The trend of D/G versus metallicity using depletion in local systems is similar to that inferred in Damped Lyα systems from abundance ratios but lies higher than the trend inferred from far-IR measurements in nearby galaxies.

Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope’s (HST) Wide Field Camera 3 and the Very Large Telescope’s Multi Unit Spectroscopic Explorer, we extend the gas-phase mass–metallicity relation (MZR) at z ≈ 1–2 down to stellar masses of M ⋆ ≈ 107.5 M ⊙. The sample reaches 6 times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 ≈ 7.8 ± 0.1 (15% solar) at log(M ⋆/M ⊙) ≈ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O iii] λ4363 and [O iii] λ1666 detections, and find excellent agreement between the techniques. The [O iii] λ1666-based metallicities double existing measurements with a signal-to-noise ratio ≥ 5 for unlensed sources at z > 1, validating the strong-line calibrations up to z ∼ 2.5. We confirm that the MZR resides ∼0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation if the low-mass slope varies with SFR. At lower redshifts (z ∼ 0.5) our sample reaches ∼0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only an ∼0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes.

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲ z ≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O vi and Ne viii absorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs at z QSO ≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated O vi λ λ 1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s−1, while the rest show no trace of O vi to a detection limit of logNOVI/cm−2≈13.7 . Meanwhile, only five galaxies or galaxy groups exhibit the Ne viii λ λ 770, 780 doublet absorption, down to a limiting column density of logNNeVIII/cm−2≈14.0 . These O vi- and Ne viii-bearing halos reside in different galaxy environments with stellar masses ranging from logMstar/M⊙≈8 to ≈11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with logMstar/M⊙≈9–11 show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O vi absorption is broad with σ υ > 40 km s−1 for galaxies of logMstar/M⊙>9 within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O vi and Ne viii is suggested to be the dominant phase in sub-L* galaxies with logMstar/M⊙≈9–10 based on their high ionization fractions in the CGM.

Outflowing gas from supermassive black holes in the centers of active galaxies has been postulated as a major contributor to galactic evolution. To explore the interaction between narrow-line region (NLR) outflows and their host galaxies, we use Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectra and Wide Field Camera 3 (WFC3) images of 15 nearby (z < 0.02) active galactic nuclei (AGN) to determine the extents and geometries of their NLRs. We combine new HST WFC3 continuum and [O iii] λ5007 images of 11 AGN with four archival AGN to match existing spectra from HST STIS. For the six AGN with suitable long-slit coverage of their NLRs, we use isophotal fitting of ground-based images, continuum-subtracted [O iii] images, and the STIS spectra, to resolve, measure, and de-project the gas kinematics to the plane of the host galaxy disk and distinguish NLR outflows from galaxy rotation and/or kinematically disturbed gas. We find an average [O iii] extent of ∼680 pc with a correlation between gas extent and [O iii] luminosity of R [O III] ∝ L[OIII]0.39 . The measured extents depend strongly on the depth of the [O iii] images, highlighting the importance of adopting uniform thresholds when analyzing scaling relationships. The outflows reach from 39% to 88% of the full NLR extents, and we find that all six of the AGN with STIS coverage of their entire NLRs show strong kinematic evidence for outflows, despite previous uncertainty for these AGN. This suggests that NLR outflows are ubiquitous in moderate-luminosity AGN and that standard criteria for kinematic modeling are essential for identifying outflows.

We present deep UV imaging observations of the Great Observatories Origins Survey Northern (GOODS-N) field with AstroSat/UVIT (AstroSat UV Deep Field north—AUDFn), using one far-UV (FUV) (F154W, 34.0 ks) and two near-UV (NUV) filters (N242W, 19.2 ks; N245M, 15.5 ks). The nature of the UV sky background was explored across the UVIT field, and a global mean and rms were estimated for each filter. We reach 3σ detection limits of m AB ∼ 27.35, 27.28, and 27.02 mag for a point source in the F154W, N242W, and N245M bands respectively. The 50% completeness limits of the FUV and NUV images are m AB = 26.40 and 27.05 mag respectively. We constructed point-spread functions for each band and estimated their FWHM, which were found to be almost the same: 1.″18 in F154W, 1.″11 in N242W, and 1.″24 in N245M. We used SExtractor to separately identify sources in the FUV and NUV filters and produce the UV source catalog of the entire AUDFn field. The source count slope estimated in FUV and NUV is 0.57 dex mag−1 (between 19 and 25 mag) and 0.44 dex mag−1 (between 18 and 25 mag), respectively. The catalog contains 6839 and 16,171 sources (brighter than the 50% completeness limit) in the FUV and NUV, respectively. Our FUV and NUV flux measurements of the identified sources complement existing multiband data in the GOODS-N field, and enable us to probe rest-frame FUV properties of galaxies at redshift z < 1 and search for candidate Lyman continuum leakers at redshift z > 0.97.