Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005hia....13..581c&link_type=abstract
In: Highlights of Astronomy, Vol. 13, as presented at the XXVth General Assembly of the IAU - 2003 [Sydney, Australia, 13 - 26 J
Astronomy and Astrophysics
Astronomy
Damped Lyman-Alpha Systems
Scientific paper
We present results from recent deep searches for HI 21cm absorption in high redshift Damped Lyman-alpha systems (DLAs). 21cm observations coupled with measurements of the total HI column density from the Lyman-alpha line allow one to estimate the average spin temperature Ts of the neutral hydrogen in the DLA. In most astrophysical circumstances the spin temperature is the same as the kinetic temperature for a single homogeneous HI cloud. In a heterogeneous medium the average spin temperature allows one to estimate the fractional HI content in different temperature phases (i.e. WNM and CNM). We will discuss the variation in the average spin temperature with redshift as well as morphology of the optical counterpart. Dwarf galaxies are known to contain a larger fraction of their atomic gas in the WNM phase so variations of the average spin temperature with morphological type of the optical counterpart could be expected. Finally we will present preliminary results of a new survey which attempts to relate the spin temperature of an absorber to its metallicity (i.e. its [Zn/H] ratio).
Chengalur Jayaram
Kanekar Nissim
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