HI content, metallicities and spin temperatures of damped and sub-damped Lyman alpha systems in the redshift desert (0.6 < z < 1.7)

Abstract

The HI 21cm absorption optical depth and the N(HI) derived from Lya absorption can be combined to yield the spin temperature (Ts) of DLAs. Although Ts measurements exist for samples of DLAs with z <0.6 and z >1.7, the intermediate redshift regime currently contains only 2 HI 21cm detections, leading to a `redshift desert' that spans 4 Gyrs of cosmic time. To connect the low and high z regimes, we present observations of the Lya line of six 0.6<z<1.7 HI 21cm absorbers. The dataset is complemented by both VLBA observations (to derive the absorber covering factor, f), and optical echelle spectra from which metal abundances are determined. Our dataset therefore not only offers the largest statistical study of HI 21cm absorbers to date, and bridges the redshift desert, but is also the first to use a fully f-corrected dataset to look for metallicity-based trends. In agreement with trends found in Galactic sightlines, we find that the lowest N(HI) absorbers tend to be dominated by warm gas. In the DLA regime, spin temperatures show a wider range of values than Galactic data, as may be expected in a heterogenous galactic population. However, we find that low metallicity DLAs are dominated by small cold gas fractions and only absorbers with relatively high metallicities exhibit significant fractions of cold gas. Using a compilation of HI 21cm absorbers which are selected to have f-corrected spin temperatures, we confirm an anti-correlation between metallicity and Ts at 3.4 sigma significance. Finally, one of the DLAs in our sample is a newly-discovered HI 21cm absorber (at z=0.602 towards J1431+3952), which we find to have the lowest f-corrected spin temperature yet reported in the literature: Ts=90+-23 K. The observed distribution of Ts and metallicities in DLAs and the implications for understanding the characteristics of the interstellar medium in high redshift galaxies are discussed.

Accepted for publication in MNRAS

References in corpus (26)

• Clustering of High Redshift ($z\ge 2.9$) Quasars from the Sloan Digital Sky Survey
• On the (Non)Evolution of HI Disks over Cosmic Time
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• Galaxy Counterparts of metal-rich Damped Lyman-alpha Absorbers - I: The case of the z=2.35 DLA towards Q2222-0946
• The Ucsd/Keck Damped Lya Abundance Database: A Decade of High Resolution Spectroscopy
• The Keck+Magellan Survey for Lyman Limit Absorption I: The Frequency Distribution of Super Lyman Limit Systems
• The End of Helium Reionization at z~2.7 Inferred from Cosmic Variance in HST/COS HeII Lyman Alpha Absorption Spectra
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems
• The Metal-Strong Damped Lyman-alpha Systems
• The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System
• Excitation mechanisms in newly discovered H2-bearing Damped Lyman-alpha clouds: systems with low molecular fractions
• Detection of the 2175Å~ extinction feature and 21-cm absorption in two MgII systems at z~1.3
• The SDSS-DR5 Survey for Proximate Damped Lya Systems
• An efficient technique for pre-selecting low redshift damped Lyman alpha systems
• Metal abundances at z<1.5: new measurements in sub-Damped Lyman-alpha Absorbers
• HI 21cm Absorption at $z\sim 2.347$ towards PKS B0438-436
• The detectability of HI 21-cm absorption in damped Lyman-alpha systems
• HI 21cm absorption at $z\sim 3.39$ towards PKS 0201+113
• On the Absence of High Metallicity-High Column Density Damped Lyman Alpha Systems: Molecule Formation in a Two-Phase Interstellar Medium
• Discovery of 21cm absorption in a $z_{\mathrm{abs}}=2.289$ DLA towards TXS 0311+430: The first low spin temperature absorber at z > 1
• HE 0515-4414 - an unusual sub-damped Ly alpha system revisited
• A Shot in the Dark: A Technique for Locating the Stellar Counterparts of Damped Lyman Alpha Absorbers
• Detecting cold gas at intermediate redshifts: GMRT survey using Mg II systems
• The kinematic signature of damped Lyman alpha systems: Using the D-index to screen for high column density HI absorbers
• 9.7 micrometer Silicate Absorption in a Damped Lyman-alpha Absorber at z=0.52
• Towards Understanding the Mass-Metallicity relation of Quasar Absorbers: Evidence for bimodality and consequences

Cited by in corpus (32)

• Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3
• The Bimodal Metallicity Distribution of the Cool Circumgalactic Medium at z<1
• A new, precise measurement of the primordial abundance of Deuterium
• Mass-metallicity relation from z=5 to the present: Evidence for a transition in the mode of galaxy growth at z=2.6 due to the end of sustained primordial gas infall
• The spin temperature of high-redshift damped Lyman-$\alpha$ systems
• The cosmic evolution of dust-corrected metallicity in the neutral gas
• The ESO UVES Advanced Data Products Quasar Sample - VI. Sub-Damped Lyman-$\alpha$ Metallicity Measurements and the Circum-Galactic Medium
• Directly imaging damped Ly-alpha galaxies at z>2. III: The star formation rates of neutral gas reservoirs at z~2.7
• The Statistical Properties of Neutral Gas at z<1.65 from UV Measurements of Damped Lyman Alpha Systems
• The COS CGM Compendium. II: Metallicities of the Partial and Lyman Limit Systems at z<1
• The chemistry of the most metal-rich damped Lyman $\alpha$ systems at z$\sim 2$ II. Context with the Local Group
• On the mass-metallicity relation, velocity dispersion and gravitational well depth of GRB host galaxies
• A comparative study of intervening and associated HI 21-cm absorption profiles in redshifted galaxies
• New HI 21-cm absorbers at low and intermediate redshifts
• A successful search for intervening 21 cm HI absorption in galaxies at 0.4 < z <1.0 with the Australian Square Kilometre Array Pathfinder (ASKAP)
• Using 21-cm absorption surveys to measure the average HI spin temperature in distant galaxies
• Keck and VLT Observations of Super-damped Lyman-alpha Absorbers at z=2=2.5: Constraints on Chemical Compositions and Physical Conditions
• An ASKAP survey for HI absorption towards dust-obscured quasars
• The most metal-rich damped Lyman alpha systems at z>1.5 I: The Data
• Simulating extremely metal-poor gas and DLA metal content at redshift z=7
• Giant Metrewave Radio Telescope detection of two new HI 21cm absorbers at $z\approx 2$
• A search for HI 21cm absorption towards a radio-selected quasar sample II: a new low spin temperature DLA at high redshift
• A statistical measurement of the HI spin temperature in DLAs at cosmological distances
• The evolution of cold neutral gas and the star formation history
• A possible connection between the spin temperature of damped Lyman-alpha absorption systems and star formation history
• A search for H$\alpha$ emission in high-metallicity damped Lyman-$\alpha$ systems at $z\sim 2.4$
• An investigation of the line of sight towards QSO PKS 0237-233
• A Search for Boron in Damped Lyα Systems
• Stringent constraints on the H I spin temperature in two z > 3 Damped Lyman-alpha systems from redshifted 21 cm absorption studies
• The potential of tracing the star formation history with HI 21-cm in intervening absorption systems
• Emergence of a new HI 21-cm absorption component at z~1.1726 towards the gamma-ray blazar PKS~2355-106
• From Exoplanets to Quasars: Detection of Potential Damped Lyman Alpha Absorbing Galaxies Using Angular Differential Imaging