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Title: HI 21 cm absorption at z ~ 2.347 towards PKS B0438-436
Authors: Kanekar, N.
Subrahmanyan, Ravi
Ellison, S.L.
Lane, W.M.
Chengalur, J.N.
Keywords: galaxies: high-redshift
galaxies: ISM
adio lines
Issue Date: Jul-2006
Publisher: Blackwell Publishing for the Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society: Letters, Vol, 370, p. L46-L50
Abstract: We report the detection of redshifted HI 21-cm absorption in the z ~ 2.347 damped Lyman α absorber (DLA) towards PKS B0438-436 with the Green Bank Telescope. This is the second-highest redshift at which 21-cm absorption has been detected in a DLA. The absorption extends over ~60 km s-1 and has two distinct components, at z = 2.347477(12) and z = 2.347869(20). A similar velocity structure is seen in optical metal lines, although the peak absorption here is offset by ~11 km s-1 from the peak in the 21-cm line. We obtain a high spin temperature Ts ~ (886 +/- 248) × (f/0.58) K, using a covering factor estimated from 2.3-GHz very long baseline interferometry data. However, the current data cannot rule out a low spin temperature. The non-detection of CO 3-2 absorption places the upper limit NCO < 3.8 × 1015 (Tx/10) cm-2 on the CO column density.
Description: Restricted Access.
ISSN: 0035-8711
1365-2966 (Online)
Alternative Location: 10.1111/j.1745-3933.2006.00186.x
Copyright: 2006 Royal Astronomical Society
Appears in Collections:Research Papers (A&A)

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