A search for HI 21cm absorption towards a radio-selected quasar sample II: a new low spin temperature DLA at high redshift

Abstract

We report results from a deep search for redshifted HI 21cm absorption from eight damped Lyman-$\alpha$ absorbers (DLAs) detected in our earlier optical survey for DLAs towards radio-loud quasars. HI 21cm absorption was detected from the $z=2.192$ DLA towards TXS2039+187, only the sixth case of such a detection at $z>2$, while upper limits on the HI 21cm optical depth were obtained in six other DLAs at $z>2$. Our detection of HI 21cm absorption in the eighth system, at $z=2.289$ towards TXS0311+430, has been reported earlier. We also present high spatial resolution images of the background quasars at frequencies close to the redshifted HI 21cm line frequency, allowing us to estimate the covering factor of each DLA, and then determine its spin temperature $T_s$. For three non-detections of HI 21cm absorption, we obtain strong lower limits on the spin temperature, $T_s\gtrsim 790$ K, similar to the bulk of the high-$z$ DLA population; three other DLAs yield weak lower limits, $T_s>140-400$ K. However, for the two DLAs with detections of HI 21cm absorption, the derived spin temperatures are both low $T_s=(160\pm 35)\times (f/0.35)$ K for the $z=2.192$ DLA towards TXS2039+187 and $T_s=(72\pm 18)\times (f/0.52)$ K for the $z=2.289$ DLA towards TXS0311+430. These are the first two DLAs at $z>1$ with $T_s$ values comparable to those obtained in local spiral galaxies. Based on the observed correlations between spin temperature and metallicity and velocity spread and metallicity in DLAs, we suggest that the hosts of the two absorbers are likely to be massive, high-metallicity galaxies.

8 pages, 4 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society

References in corpus (11)

• On the (Non)Evolution of HI Disks over Cosmic Time
• Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• On the Nature of Velocity Fields in High z Galaxies
• The Ucsd/Keck Damped Lya Abundance Database: A Decade of High Resolution Spectroscopy
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems
• HI 21cm Absorption at $z\sim 2.347$ towards PKS B0438-436
• HI 21cm absorption at $z\sim 3.39$ towards PKS 0201+113
• HI content, metallicities and spin temperatures of damped and sub-damped Lyman alpha systems in the redshift desert (0.6 < z < 1.7)
• 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
• A search for damped Lyman-alpha systems towards radio-loud quasars I: The optical survey

Cited by in corpus (15)

• The spin temperature of high-redshift damped Lyman-$\alpha$ systems
• A comparative study of intervening and associated HI 21-cm absorption profiles in redshifted galaxies
• Invisible Active Galactic Nuclei. II Radio Morphologies & Five New HI 21 cm Absorption Line Detections
• Using 21-cm absorption surveys to measure the average HI spin temperature in distant galaxies
• Giant Metrewave Radio Telescope detection of two new HI 21cm absorbers at $z\approx 2$
• Real-time RFI Filtering for uGMRT: Overview of the Released System and Relevance to the SKA
• 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
• 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
• Cold neutral hydrogen gas in galaxies
• The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C82
• Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities
• From Exoplanets to Quasars: Detection of Potential Damped Lyman Alpha Absorbing Galaxies Using Angular Differential Imaging