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Abundances of chemical elements in the interstellar and circumgalactic media of high-redshift galaxies offer important constraints on the nucleosynthesis by early generations of stars. Damped Lyαabsorbers (DLAs) in spectra of high-redshift background quasars are excellent sites for obtaining robust measurements of element abundances in distant galaxies. Past studies of DLAs at redshiftsz> 4 have measured abundances of ≲0.01 solar. Here we report the discovery of a DLA atz= 4.7372 with an exceptionally high degree of chemical enrichment. We estimate the Hicolumn density in this absorber to be log (N_{H I}/cm⁻²) = 20.48 ± 0.15. Our analysis shows unusually high abundances of carbon and oxygen ([C/H] = 0.88 ± 0.17, [O/H] = 0.71 ± 0.16). Such a high level of enrichment a mere 1.2 Gyr after the Big Bang is surprising because of insufficient time for the required amount of star formation. To our knowledge, this is the first supersolar absorber found atz> 4.5. We find the abundances of Si and Mg to be [Si/H] =$-{0.56}_{-0.35}^{+0.40}$and [Mg/H] =${0.59}_{-0.50}^{+0.27}$, confirming the metal-rich nature of this absorber. By contrast, Fe shows a much lower abundance ([Fe/H] =$-{1.53}_{-0.15}^{+0.15}$). We discuss implications of our results for galactic chemical evolution models. The metallicity of this absorber is higher than that of any other known DLA and is >2 orders of magnitude above predictions of chemical evolution models and theN_{H I}-weighted mean metallicity from previous studies atz> 4.5. The relative abundances (e.g., [O/Fe] = 2.29 ± 0.05, [C/Fe] = 2.46 ± 0.08) are also highly unusual compared to predictions for enrichment by early stars.

 

We analyze the cool gas in and around 14 nearby galaxies (atz< 0.1) mapped with the Sloan Digital Sky Survey IV MaNGA survey by measuring absorption lines produced by gas in spectra of background quasars/active galactic nuclei at impact parameters of 0–25 effective radii from the galactic centers. Using Hubble Space Telescope/Cosmic Origins Spectrograph, we detect absorption at the galactic redshift and measure or constrain column densities of neutral (Hi, Ni, Oi, and Ari), low-ionization (Siii, Sii, Cii, Nii, and Feii), and high-ionization (Siiii, Feiii, Nv, and Ovi) species for 11 galaxies. We derive the ionization parameter and ionization-corrected metallicity usingcloudyphotoionization models. The Hicolumn density ranges from ∼10¹³to ∼10²⁰cm⁻²and decreases with impact parameter forr≳R_e. Galaxies with higher stellar mass have weaker Hiabsorption. Comparing absorption velocities with MaNGA radial velocity maps of ionized gas line emissions in galactic disks, we find that the neutral gas seen in absorption corotates with the disk out to ∼10R_e. Sight lines with lower elevation angles show lower metallicities, consistent with the metallicity gradient in the disk derived from MaNGA maps. Higher-elevation angle sight lines show higher ionization, lower Hicolumn density, supersolar metallicity, and velocities consistent with the direction of galactic outflow. Our data offer the first detailed comparisons of circumgalactic medium (CGM) properties (kinematics and metallicity) with extrapolations of detailed galaxy maps from integral field spectroscopy; similar studies for larger samples are needed to more fully understand how galaxies interact with their CGM.

 

ABSTRACT We present abundance measurements of the elements Zn, S, O, C, Si, and Fe for four sub-DLAs at redshifts ranging from z = 2.173 to 2.635 using observations from the MIKE spectrograph on the Magellan telescope to constrain the chemical enrichment and star formation of gas-rich galaxies. Using weakly depleted elements O, S, and or Zn, we find the metallicities after the photoionization corrections to be [S/H] = −0.50 ± 0.11, [O/H] > −0.84, [O/H] = −1.27 ± 0.12, and [Zn/H]  = +0.40 ± 0.12 for the absorbers at z  = 2.173, 2.236, 2.539, and 2.635, respectively. Moreover, we are able to put constraints on the electron densities using the fine structure lines of C ii⋆ and Si ii⋆ for two of the sub-DLAs. We find that these values are much higher than the median values found in DLAs in the literature. Furthermore, we estimate the cooling rate lc = 1.20 × 10−26 erg s−1 per H atom for an absorber at z = 2.173, suggesting higher star formation rate density in this sub-DLA than the typical star formation rate density for DLAs at similar redshifts. We also study the metallicity versus velocity dispersion relation for our absorbers. Most of the absorbers follow the trend one can expect from the mass versus metallicity relation for sub-DLAs in the literature. Finally, we are able to put limits on the molecular column density from the non-detections of various strong lines of CO molecules. We estimate 3σ upper limits of logN(CO, J = 0) < 13.87, logN(CO, J = 0) < 13.17, and logN(CO, J = 0) < 13.08, respectively, from the non-detections of absorption from the J = 0 level in the CO AX 0–0, 1–0, and 2–0 bands near 1544, 1510, and 1478 Å.