New searches for HI 21-cm in damped Lyman-alpha absorption systems

Abstract

We present the results of three separate searches for HI 21-cm absorption in a total of twelve damped Lyman-alpha absorption systems (DLAs) and sub-DLAs over the redshift range z = 0.86-3.37. We find no absorption in the five systems for which we obtain reasonable sensitivities and add the results to those of other recent surveys in order to investigate factors which could have an effect on the detection rate: We provide evidence that the mix of spin temperature/covering factor ratios seen at low redshift may also exist at high redshift, with a correlation between the 21-cm line strength and the total neutral hydrogen column density, indicating a roughly constant spin temperature/covering factor ratio for all of the DLAs searched. Also, by considering the geometry of a flat expanding Universe together with the projected sizes of the background radio emission regions, we find, for the detections, that the 21-cm line strength is correlated with the size of the absorber. For the non-detections it is apparent that larger absorbers (covering factors) are required in order to exhibit 21-cm absorption, particularly if these DLAs do not arise in spiral galaxies. We also suggest that the recent z = 2.3 detection towards TXS 0311+430 arises in a spiral galaxy, but on the basis of a large absorption cross-section and high metallicity, rather than a low spin temperature

11 pages, accepted by MNRAS

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Cited by in corpus (27)

• The spin temperature of high-redshift damped Lyman-$\alpha$ systems
• Search for cold gas in z>2 damped Lyman-alpha systems: 21-cm and H_2 absorption
• Search for cold gas in strong MgII absorbers at 0.5<z<1.5: nature and evolution of 21-cm absorbers
• Complete ionisation of the neutral gas: why there are so few detections of 21-cm hydrogen in high redshift radio galaxies and quasars
• A Giant Metrewave Radio Telescope survey for associated HI 21-cm absorption in the Caltech-Jodrell Flat-spectrum sample
• HI content, metallicities and spin temperatures of damped and sub-damped Lyman alpha systems in the redshift desert (0.6 < z < 1.7)
• 21-cm absorption from galaxies at z ~ 0.3
• The geometry effects of an expanding Universe on the detection of cool neutral gas at high redshift
• HI 21-cm absorption survey of quasar-galaxy pairs: Distribution of cold gas around z<0.4 galaxies
• New HI 21-cm absorbers at low and intermediate redshifts
• On the detectability of HI 21-cm in MgII absorption system
• Revealing HI gas in emission and absorption on pc to kpc scales in a galaxy at z ~ 0.017
• Giant Metrewave Radio Telescope detection of associated HI 21cm absorption at $z=1.2230$ towards TXS1954+513
• Incidence of HI 21-cm absorption in strong FeII systems at $0.5<z<1.5$
• MALS-NOT: Identifying Radio-Bright Quasars for the MeerKAT Absorption Line Survey
• Dissecting cold gas in a high-redshift galaxy using a lensed background quasar
• Localised HI 21-cm absorption towards a double-lobed z=0.24 radio galaxy
• The evolution of cold neutral gas and the star formation history
• HI 21-cm absorption from $z\sim 0.35$ strong MgII absorbers
• Nature of the DLA towards Q0528-250: High pressure and strong UV field revealed by excitation of CI, H2 and SiII
• 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
• Probing galaxy evolution through HI 21-cm emission and absorption: current status and prospects with the Square Kilometre Array
• The potential of tracing the star formation history with HI 21-cm in intervening absorption systems
• Cold neutral hydrogen gas in galaxies
• A third HI 21-cm absorption system in the sight-line of MG J0414+0534: A redshift for Object X?
• Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities