N. Kanekar et Jn. Chengalur, ORT OBSERVATIONS OF THE DAMPED LYMAN-ALPHA SYSTEM TOWARDS PKS-0201+113, Monthly Notices of the Royal Astronomical Society, 292(4), 1997, pp. 831-834
We report a deep radio search with the Ooty Radio Telescope (ORT) for
the redshifted 21-cm absorption line from the damped Lyman a system se
en at redshift 3.388 against the quasar PKS 0201 + 113. This is curren
tly the most distant system for which a detection of the 21-cm absorpt
ion line has been claimed. The present observations have a sensitivity
comparable to the earlier ones and detect no statistically significan
t absorption. We use the non-detection to place an upper limit of simi
lar to 0.011 on the optical depth of the damped Lyman a absorber. This
corresponds to a lower limit of similar to 5600K to the spin temperat
ure of the system. This is considerably higher than the previous upper
limit of similar to 1380 K.