ALBERT

Description: We present chemical abundance measurements from high-resolution observations of five sub-damped Lyman α absorbers (sub-DLAs) 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 near-solar or supersolar. We also investigate the effect of ionization on the observed abundances using photoionization modelling. Combining our data with other sub-DLA and DLA data from the literature, we report the most complete existing determination of the metallicity versus redshift relation for sub-DLAs and DLAs. We confirm the suggestion from previous investigations that sub-DLAs are, on average, more metal rich than DLAs and may evolve faster. We also discuss relative abundances and abundance ratios in these absorbers. The more metal-rich systems show significant dust depletion levels, as suggested by the ratios [Zn/Cr] and [Zn/Fe]. For the majority of the systems in our sample, the [Mn/Fe] versus [Zn/H] trend is consistent with that seen previously for lower redshift sub-DLAs. We also measure the velocity width values for the sub-DLAs in our sample from unsaturated absorption lines of Fe ii 2344, 2374, 2600 Å, and examine where these systems lie in a plot of metallicity versus velocity dispersion. Finally, we examine cooling rate versus H i column density in these sub-DLAs, and compare this with the data from DLAs and the Milky Way interstellar medium. We find that most of the systems in our sample show higher cooling rate values compared to those seen in the DLAs.

Description: The circumgalactic medium (CGM) can be probed through the analysis of absorbing systems in the line of sight to bright background quasars. We present measurements of the metallicity of a new sample of 15 sub-damped Lyman α absorbers (sub-DLAs, defined as absorbers with 19.0 〈 log N(H I) 〈 20.3) with redshift 0.584 ≤ z abs ≤ 3.104 from the ESO Ultra-Violet Echelle Spectrograph (UVES) Advanced Data Products Quasar Sample (EUADP). We combine these results with other measurements from the literature to produce a compilation of metallicity measurements for 92 sub-DLAs as well as a sample of 362 DLAs. We apply a multi-element analysis to quantify the amount of dust in these two classes of systems. We find that either the element depletion patterns in these systems differ from the Galactic depletion patterns or they have a different nucleosynthetic history than our own Galaxy. We propose a new method to derive the velocity width of absorption profiles, using the modelled Voigt profile features. The correlation between the velocity width V 90 of the absorption profile and the metallicity is found to be tighter for DLAs than for sub-DLAs. We report hints of a bimodal distribution in the [Fe/H] metallicity of low redshift ( z 〈 1.25) sub-DLAs, which is unseen at higher redshifts. This feature can be interpreted as a signature from the metal-poor, accreting gas and the metal-rich, outflowing gas, both being traced by sub-DLAs at low redshifts.

Description: Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay Telescope, we target candidate absorption host galaxies detected in deep optical imaging (reaching limiting apparent magnitudes of 23.0–26.5 in g , r , i , and z filters) in the fields of three QSOs, each of which shows the presence of high metallicity, high $N_{\rm H\,\small {i}}$ absorption systems in their spectra (Q0826-2230: z abs = 0.9110, Q1323-0021: z abs = 0.7160, Q1436-0051: z abs = 0.7377, 0.9281). We confirm three host galaxies at redshifts 0.7387, 0.7401, and 0.9286 for two of the Lyman α absorption systems (one with two galaxies interacting). For these systems, we are able to determine the star formation rates (SFRs); impact parameters (from previous imaging detections); the velocity shift between the absorption and emission redshifts; and, for one system, also the emission metallicity. Based on previous photometry, we find these galaxies have L 〉 L *. The [O ii ] SFRs for these galaxies are in the range 11–25 M  yr –1 (uncorrected for dust), while the impact parameters lie in the range 35–54 kpc. Despite the fact that we have confirmed galaxies at 50 kpc from the QSO, no gradient in metallicity is indicated between the absorption metallicity along the QSO line of sight and the emission line metallicity in the galaxies. We confirm the anticorrelation between impact parameter and $N_{\rm H\,\small {i}}$ from the literature. We also report the emission redshift of five other galaxies: three at z em 〉 z QSO , and two ( L 〈 L *) at z em 〈 z QSO not corresponding to any known absorption systems.

Description: We present global VLBI observations of the 21-cm transition of atomic hydrogen seen in absorption against the radio source J0855+5751. The foreground absorber (SDSS J085519.05+575140.7) is a dwarf galaxy at z  = 0.026. As the background source is heavily resolved by VLBI, the data allow us to map the properties of the foreground H i gas with a spatial resolution of 2 pc. The absorbing gas corresponds to a single coherent structure with an extent 〉35 pc, but we also detect significant and coherent variations, including a change in the H i optical depth by a factor of 5 across a distance of 6 pc. The large size of the structure provides support for the Heiles & Troland model of the interstellar medium, as well as its applicability to external galaxies. The large variations in H i optical depth also suggest that caution should be applied when interpreting T S measurements from radio-detected DLAs. In addition, the distorted appearance of the background radio source is indicative of a strong jet–cloud interaction in its host galaxy. We have measured its redshift ( z  = 0.541 86) using optical spectroscopy on the William Herschel Telescope and this confirms that J0855+5751 is an FR II radio source with a physical extent of 〈1 kpc and supports the previous identification of this source as a compact symmetric object. These sources often show absorption associated with the host galaxy and we suggest that both H i and OH should be searched for in J0855+5751.

Description: The use of background quasars provides a powerful tool to probe the cool gas in the circumgalactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z = 0.7–1. We report the detection with both instruments of the Hα emission line of one sub-damped Lyman α (sub-DLA) at z abs = 0.941 87 with $\log N({\rm H}\,{\small {I}})$ = 19.38 $^{+0.10}_{-0.15}$ towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR = 3.6 ± 2.2 M  yr –1 in that system. A detailed kinematic study indicates a dynamical mass M dyn = 10 9.9±0.4 M and a halo mass M halo = 10 11.9±0.5 M . In addition, we report the [O ii ] detection with X-Shooter of another DLA at z abs = 0.7402 with $\log N({\rm H}\,{\small {I}})$ = 20.4 ± 0.1 towards Q0052+0041 and an estimated SFR of 5.3 ± 0.7 M  yr –1 . Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might be at the redshift of the quasar. We use the objects detected in our whole $N({\rm H}\,{\small {I}})$ -selected SINFONI survey to compute the metallicity difference between the galaxy and the absorbing gas, $\delta _{\rm H\,\small {I}}(X)$ , where a positive (negative) value indicates infall (outflow). We compare this quantity with the quasar line-of-sight alignment with the galaxy's major (minor) axis, another tracer of infall (outflow). We find that these quantities do not correlate as expected from simple assumptions. Additional observations are necessary to relate these two independent probes of gas flows around galaxies.

Description: In this work, we study argon abundances in the interstellar medium of high-redshift galaxies (2.0 ≤  z abs  ≤ 4.2) detected as damped Lyα absorbers (DLA) in the spectra of background quasars. We use high-resolution quasar spectra obtained from the European Southern Observatory Ultraviolet-Visual Echelle Spectrograph Advanced Data Products data base. We present three new measurements and five upper limits of Ar i . We further compiled DLAs/sub-DLA data from the literature with measurements available of argon and α-capture elements (S or Si), making up a total of 37 systems, i.e. the largest DLA argon sample investigated so far. We confirm that argon is generally deficient in DLAs, with a mean value [Ar/α] ~= –0.4 ± 0.06 dex (standard error of the mean). The [Ar/α] ratios show a weak, positive trend with increasing H i column density and increasing absorption redshift, and a weak, negative trend with dust-free metallicity, [S/H]. Detailed analysis of the abundance ratios indicates that Ar i ionization, rather than dust depletion or nucleosynthetic evolution, is responsible for the argon deficiency. Altogether, the observational evidence is consistent with a scenario of argon ionization dominated by quasar metagalactic radiation modulated by local H i self-shielding inside the DLA host galaxies. Our measurements and limits of argon abundances suggest that the cosmic reionization of He ii is completed above z  ~ 3, but more measurements at z abs  〉 3.5 are required to probe the final stages of this process of cosmic reionization.

Description: We report here a study of nitrogen and α-capture element (O, S, and Si) abundances in 18 damped Lyα absorbers (DLAs) and sub-DLAs drawn from the European Southern Observatory's Ultraviolet Visual Echelle Spectrograph (ESO-UVES) Advanced Data Products (EUADP) data base. We report nine new measurements, five upper and four lower limits of nitrogen that when compiled with available nitrogen measurements from the literature makes a sample of 108 systems. The extended sample presented here confirms the [N/α] bimodal behaviour suggested in previous studies. Three-quarter of the systems show 〈[N/α]〉 = –0.85 (±0.20 dex) and one-quarter of the systems show that ratios are clustered at 〈[N/α]〉 = –1.41 (±0.14 dex). The high [N/α] plateau is consistent with the H ii regions of dwarf irregular and blue compact dwarf galaxies although extended to lower metallicities and could be interpreted as the result of a primary nitrogen production by intermediate mass stars. The low [N/α] values are the lowest ever observed in any astrophysical site. In spite of this fact, even lower values could be measured with the present instrumentation, but we do not find them below [N/α] –1.7. This suggests the presence of a floor in [N/α] abundances, which along with the lockstep increase of N and Si may indicate a primary nitrogen production from fast rotating, massive stars in relatively young or unevolved systems.

Description: The circumgalactic medium (CGM) of typical galaxies is crucial to our understanding of the cycling of gas into, through and out of galaxies. One way to probe the CGM is to study gas around galaxies detected via the absorption lines they produce in the spectra of background quasars. Here, we present medium resolution and new ~0.4-arcsec resolution (~3 kpc at z  ~ 1) 3D observations with Very Large Telescope/Spectrograph for Integral Field Observations in the Near Infrared of galaxies responsible for high- N (H i ) quasar absorbers. These data allow us to determine in details the kinematics of the objects: the four z  ~ 1 objects are found to be rotation supported as expected from inclined discs, while the fifth z  ~ 2 system is dispersion dominated. Two of the systems show sign of interactions and merging. In addition, we use several indicators (star formation per unit area, a comparison of emission and absorption kinematics, arguments based on the inclination and the orientation of the absorber to the quasar line of sight and the distribution of metals) to determine the direction of the gas flows in and out of these galaxies. In some cases, our observations are consistent with the gas seen in absorption being due to material corotating with their haloes. In the case of absorbing galaxies towards Q1009–0026 and Q2222–0946, these indicators point towards the presence of an outflow traced in absorption.

Description: We present the study of a sample of nine quasi-stellar object fields, with damped Lyman α (DLA) or sub-DLA systems at z ~ 0.6, observed with the X-Shooter spectrograph at the Very Large Telescope. By suitably positioning the X-Shooter slit based on high spatial resolution images of Hubble Space Telescope /Advanced Camera for Surveys we are able to detect absorbing galaxies in seven out of nine fields (~78 per cent success rate) at impact parameters from 10 to 30 kpc. In five out of seven fields the absorbing galaxies are confirmed via detection of multiple emission lines at the redshift of DLAs where only one out of five also emits a faint continuum. In two out of these five fields we detect a second galaxy at the DLA redshift. Extinction corrected star formation rates (SFRs) of these DLA galaxies, estimated using their Hα fluxes, are in the range 0.3–6.7 M  yr –1 . The emission metallicities of these five DLA galaxies are estimated to be from 0.2 to 0.9 Z . Based on the Voigt profile fits to absorption lines we find the metallicity of the absorbing neutral gas to be in a range of 0.05–0.6 Z . The two remaining DLA galaxies are quiescent galaxies with SFR 〈 0.4 M  yr –1 (3) presenting continuum emission but no emission lines. Using X-Shooter spectrum we estimate i -band absolute magnitude of –19.5 ± 0.2 for both these DLA galaxies that indicates they are sub-L * galaxies. Comparing our results with that of other surveys in the literature we find a possible redshift evolution of the SFR of DLA galaxies.