Stringent constraints on the H I spin temperature in two z > 3 Damped Lyman-alpha systems from redshifted 21 cm absorption studies

Abstract

Physical properties of Damped Lyman-alpha absorbers and their evolution are closely related to galaxy formation and evolution theories, and have important cosmological implications. H I 21 cm absorption study is one useful way of measuring the temperature of these systems. In this work, very strong constraints on the temperature of two Damped Lyman-alpha absorbers at z > 3 are derived from low radio frequency observations. The H I spin temperature is found to be greater than 2000 K for both the absorbers. The high spin temperature of these high-redshift systems is in agreement with the trend found in a compilation of temperatures for other Damped Lyman-alpha absorbers. We also argue that the temperature - metallicity relation, reported earlier in the literature, is unlikely to be a spurious line of sight effect, and that the redshift evolution of the spin temperature does not arises due to a selection effect. All of these are consistent with a redshift evolution of the warm gas fraction in Damped Lyman-alpha systems.

5 pages, 4 figures. Accepted for publication in MNRAS Letters. The definitive version will be available at http://mnrasl.oxfordjournals.org/

References in corpus (8)

• On the (Non)Evolution of HI Disks over Cosmic Time
• The Fundamental Plane of Damped Lyman Alpha Systems
• 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
• 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 HI 21cm absorption towards a radio-selected quasar sample II: a new low spin temperature DLA at high redshift

Cited by in corpus (7)

• The spin temperature of high-redshift damped Lyman-$\alpha$ systems
• The evolution of neutral hydrogen over the past 11 Gyr via HI 21 cm absorption
• 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
• The potential of tracing the star formation history with HI 21-cm in intervening absorption systems
• C II radiative cooling of the Galactic diffuse interstellar medium: Insight about the star formation in Damped Lyman-alpha systems
• Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities