HI 21cm absoprtion in two low redshift damped Ly-alpha systems
Abstract
We report the discovery of two low redshift HI 21cm absorbers, one at z = 0.2212 towards the zem = 0.630 quasar OI 363 (B0738+313), and the other at z = 0.3127 towards PKS B1127-145 (zem = 1.187). Both were found during a survey of MgII selected systems at redshifts 0.2 < z < 1 using the new UHF-high system at the Westerbork Synthesis Radio Telescope (WSRT). New HST/FOS observations also identify both systems as damped Ly-alpha (DLa) absorbers. By comparing the column density from the DLa line with that from the HI 21cm line, we calculate the spin temperature, and find that Ts is approximately 1000 K for both of these low redshift absorbers. We briefly discuss some implications of this result.
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