(Abbreviated) From six spectra of high-z QSOs, we select eleven metal-rich, Z>=Z_solar, and optically-thin to the ionizing radiation, N(HI)<10^17 cm^-2, absorption systems ranging between z=1.5 and z=2.9 and revealing lines of different ions in subsequent ionization stages. The majority of the systems (10 from 11) show abundance patterns which relate them to outflows from low and intermediate mass stars. All systems have sub-kpc linear sizes along the line-of-sight with many less than 20 pc. In several systems, silicon is deficient, presumably due to the depletion onto dust grains in the envelopes of dust-forming stars and the subsequent gas-dust separation. At any value of [C/H], nitrogen can be either deficient, [N/C]<0, or enhanced, [N/C]>0, which supposes that the nitrogen enrichment occurs irregularly. In some cases, the lines of MgII 2796, 2803 appear to be shifted, probably as a result of an enhanced content of heavy isotopes 25Mg and 26Mg in the absorbing gas relative to the solar isotopic composition. Seven absorbers are characterized by low mean ionization parameter U, log U<-2.3, among them only one system has a redshift z>2 whereas all others are found at z ~= 1.8. Comparing the space number density of metal-rich absorbers with the comoving density of star-forming galaxies at z ~= 2, we estimate that the circumgalactic volume of each galaxy is populated by 10^7 - 10^8 such absorbers with total mass <=1/100th of the stellar galactic mass. Possible effects of high metal content on the peak values of star-forming and AGN activities at z~2 are discussed.
MgII absorbers induce reddening on background quasars. We measure this effect and infer the cosmic density of dust residing in these systems to be Ω ~ 2e-6, in units of the critical density of the Universe, which is comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. We also estimate the neutral hydrogen abundance in MgII clouds to be Ω ~ 1.5e-4, which is approximately 5% of hydrogen in stars in galaxies. This implies a dust-to-gas mass ratio for MgII clouds of about 1/100, which is similar to the value for normal galaxies. This…
The Complete Optical and Radio Absorption Line System (CORALS) survey has previously been used to demonstrate that the number density, gas and metals content of z>1.6 damped Lyman alpha systems is not significantly under-estimated in magnitude limited surveys. In this paper, a sample of strong MgII absorbers selected from the optically complete 0.7 < z < 1.6 CORALS sample of Ellison et al. is used to assess the potential of dust bias at intermediate redshifts. From echelle spectra of all CORALS absorbers with MgII lambda 2796 and FeII lambda 2600 rest equivalent widths > 0.5 A in the redshift …
We present chemical abundance measurements from high-resolution observations of 5 sub-damped Lyman-alpha absorbers at 1.7 < z < 2.4 observed with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan II Clay telescope. Lines of Zn II, Mg I, Mg II, Al II, Al III, S II, Si II, Si IV, C II, C II*, C IV, Ni II, Mn II and Fe II were detected and column densities were determined. The metallicity of the absorbing gas, inferred from the nearly undepleted element Zn, is in the range of < -0.95 to +0.25 dex for the five absorbers in our sample, with three of the systems being ne…
The damped and sub-damped Lyman-alpha absorption line systems in quasar spectra are believed to be produced by intervening galaxies. However, the connection of quasar absorbers to galaxies is not well-understood, since attempts to image the absorbing galaxies have often failed. While most DLAs appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs, has been discovered in recent studies. Here we report high-resolution K-band imaging with the Keck Laser Guide Star Adaptive Optics (LGSAO) system of the field of quasar SDSSJ1323-0021 in search of the galaxy producing the z …
Nitrogen is thought to have both primary and secondary origins depending on whether the seed carbon and oxygen are produced by the star itself (primary) or already present in the interstellar medium (secondary) from which star forms. DLA and sub-DLA systems with typical metallicities of -3.0<Z/Z_sun<-0.5 are excellent tools to study nitrogen production. We made a search for nitrogen in the ESO-UVES advanced data products (EUADP) database. In the EUADP database, we find 10 new measurements and 9 upper limits of nitrogen. We further compiled DLA/sub-DLA data from the literature with estimates av…
We analyze relative abundances and ionization conditions in a strong absorption system at z=6.84, seen in the spectrum of the z=7.54 background quasar ULAS J134208.10+092838.61. Singly ionized C, Si, Fe, Mg, and Al measurements are consistent with a warm neutral medium that is metal-poor but not chemically pristine. Firm non-detections of C IV and Si IV imply that any warm ionized phase of the IGM or CGM has not yet been enriched past the ultra-metal-poor regime (<0.001Z_{solar}), unlike lower redshift DLAs where these lines are nearly ubiquitous. Relative abundances of the heavy elements 794 …
Context. The study of abundances in the nucleus of active galaxies allows us to investigate the evolution of abundance by comparing local and higher redshift galaxies. However, the methods used so far have substantial drawbacks or rather large uncertainties. Some of the measurements are at odds with the initial mass function derived from the older stellar population of local elliptical galaxies. Aims. We determine accurate and reliable abundances of C, N, Ne, and Fe relative to O from the narrow absorption lines observed in the X-ray spectra of Mrk 509. Methods. We use the stacked 600 ks XMM-N…
We report on the detection of three strong HI absorbers originating in the outskirts (i.e., impact parameter, $ρ_{\rm cl} \approx (1.6-4.7) r_{500}$) of three massive ($M_{500}\sim3\times10^{14} M_{\odot}$) clusters of galaxies at redshift $z_{\rm cl} \approx 0.46$, in the $Hubble Space Telescope$ Cosmic Origins Spectrograph ($HST$/COS) spectra of 3 background UV-bright quasars. These clusters were discovered by the 2500 deg$^2$ South Pole Telescope Sunyaev$-$Zel'dovich (SZ) effect survey. All three COS spectra show partial Lyman limit absorber with $N(HI) > 10^{16.5} \ \rm cm^{-2}$ near the p…
We study metal depletion due to dust in the interstellar medium (ISM) to infer the properties of dust grains and characterize the metal and dust content of galaxies, down to low metallicity and intermediate redshift z. We provide metal column densities and abundances of a sample of 70 damped Lyman-α absorbers (DLAs) towards quasars, observed at high spectral resolution with the Very Large Telescope (VLT) Ultraviolet and Visual Echelle Spectrograph (UVES). This is the largest sample of phosphorus abundances measured in DLAs so far. We use literature measurements for Galactic clouds to cover the…
We examine the abundance, clustering and metallicity of Damped Lyman-alpha Absorbers (DLAs) in a suite of hydrodynamic cosmological simulations using the moving mesh code AREPO. We incorporate models of supernova and AGN feedback, as well as molecular hydrogen formation. We compare our simulations to the column density distribution function at $z=3$, the total DLA abundance at $z=2-4$, the measured DLA bias at $z=2.3$ and the DLA metallicity distribution at $z=2-4$. Our preferred models produce populations of DLAs in good agreement with most of these observations. The exception is the DLA abun…
We estimate the abundance of dust in damped Lyman-α absorbers (DLAs) by statistically measuring the excess reddening they induce on their background quasars. We detect systematic reddening behind DLA consistent with the SMC type reddening curve, but it is inconsistent with the Milky Way type reddening. We find that the derived dust-to-gas ratio is, on average, inversely proportional to the column density of neutral hydrogen, implying that the amount of dust is constant, irrespective of the column density of hydrogen. It means that the average metallicity is inversely proportional to the column…
H I Absorbers as Beacons of Hidden Structure at $z \sim 3$: Multi-Component, Metal-Rich Absorption System near a Protocluster
The University of Tokyo（东京大学）；Shinshu University（信州大学）；Tohoku University（东北大学）；Hosei University（法政大学）；National Astronomical Observatory of Japan（日本国立天文台）
Overdense, metal-rich regions, shielded from stellar radiation might remain neutral throughout reionization and produce metal as well as 21 cm absorption lines. Simultaneous absorption from metals and 21 cm can complement each other as probes of underlying gas properties. We use Aurora, a suite of high resolution radiation-hydrodynamical simulations of galaxy formation, to investigate the occurrence of such "aligned" absorbers. We calculate absorption spectra for 21 cm, OI, CII, SiII and FeII. We find velocity windows with absorption from at least one metal and 21 cm, and classify the aligned …
We present a detailed analysis of chemical abundances in a sub-damped Lyman alpha absorber at z=1.839 towards the quasar B1101-26, based on a very-high-resolution (R ~ 75,000) and high-signal-to-noise (S/N >100) spectrum observed with the UV Visual Echelle spectrograph (UVES) installed on the ESO Very Large Telescope (VLT). The absorption line profiles are resolved into a maximum of eleven velocity components spanning a rest-frame velocity range of 200 km/s. Detected ions include CII, CIV, NII, OI, MgI, MgII, AlII, AlIII, SiII, SiIII, SiIV, FeII, and possibly SII. The total neutral hydrogen co…
We present Cosmic Origins Spectrograph (COS) measurements of metal abundances in eight 0.083<z<0.321 damped Lyman-α(DLA) and sub-damped Ly-α absorption systems serendipitously discovered in the COS-Halos survey. We find that these systems show a large range in metallicities, with -1.10<[Z/H]<0.31, similar to the spread found at higher redshifts. These low-redshift systems on average have subsolar metallicities, but do show a rise in metallicity over cosmic time when compared to higher-redshift systems. We find the average sub-DLA metallicity is higher than the average DLA metallicity at all re…
We report the detection of a strong HI 21-cm absorption system at z=0.5344, as well as a candidate system at z=0.3389, in the sight-line towards the z=2.64 quasar MG J0414+0534. This, in addition to the absorption at the host redshift and the other two intervening absorbers, takes the total to four (possibly five). The previous maximum number of 21-cm absorbers detected along a single sight-line is two and so we suspect that this number of gas-rich absorbers is in some way related to the very red colour of the background source. Despite this, no molecular gas (through OH absorption) has yet be…
Two new high-precision measurements of the deuterium abundance from absorbers along the line of sight to the quasar PKS1937--1009 were presented. The absorbers have lower neutral hydrogen column densities (N(HI) $\approx$ 18\,cm$^{-2}$) than for previous high-precision measurements, boding well for further extensions of the sample due to the plenitude of low column density absorbers. The total high-precision sample now consists of 12 measurements with a weighted average deuterium abundance of D/H = $2.55\pm0.02\times10^{-5}$. The sample does not favour a dipole similar to the one detected for …
We have initiated a survey using the newly commissioned X-shooter spectrograph to target candidate relatively metal-rich damped Lyman-alpha absorbers (DLAs). The spectral coverage of X-shooter allows us to search for not only Lyman-alpha emission, but also rest-frame optical emission lines. We have chosen DLAs where the strongest rest-frame optical lines ([OII], [OIII], Hbeta and Halpha) fall in the NIR atmospheric transmission bands. In this first paper resulting from the survey, we report on the discovery of the galaxy counterpart of the z_abs = 2.354 DLA towards the z=2.926 quasar Q2222$-09…
To explore the ionization conditions in highly-ionized absorbers at high redshift we have studied in detail two intervening OVI absorbers at z=2 towards the quasar PKS1448-232, based on high (R=75,000) and intermediate (R=45,000) resolution optical VLT/UVES spectra. We find that both absorption systems are composed of several narrow subcomponents with CIV/OVI Doppler-parameters b<10 km/s, typically. This implies that the gas temperatures are T<10^5 K and that the absorbers are photoionized by the UV background. The system at z=2.1098 represents a simple, isolated OVI absorber that has only two…
We have studied a sample of 1084 intervening absorption systems with 2.15$\le z_{ab}\le$5.2, having log(N$_{\rm HI}$) $>$ 20.0 in the spectra of QSOs in Sloan Digital Sky Survey (SDSS) data release 7 (DR7), with the aim of understanding the nature and abundance of the dust and the chemical abundances in the DLA absorbers. Composite spectra were constructed for the full sample and several subsamples, chosen on the basis of absorber and QSO properties. Average extinction curves were obtained for the samples by comparing their geometric mean composite spectra with those of two samples of QSOs, ma…
