Molecular gas at intermediate redshifts

Kanekar, N. ; Chengalur, J. N. (2002) Molecular gas at intermediate redshifts Astronomy & Astrophysics, 381 (3). L73-L76. ISSN 0004-6361

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Official URL: http://www.aanda.org/index.php?option=com_article&...

Related URL: http://dx.doi.org/10.1051/0004-6361:20011697

Abstract

We present Giant Metrewave Radio Telescope (GMRT) observations of OH absorption in B3 1504+377 ( z ~ 0.673) and PKS 1413+135 ( z ~ 0.247 ). OH has now been detected in absorption towards four intermediate redshift systems, viz. the lensing galaxies towards B 0218+357 ( z ~ 0.685; Kanekar et al. 2001) and 1830-211 ( z ~ 0.886; Chengalur et al. 1999), in addition to the two systems listed above. All four systems also give rise to well studied millimetre wavelength molecular line absorption from a host of molecules, including HCO +. Comparing our OH data with these millimetre line transitions, we find that the linear correlation between NOH and NHCO+found in molecular clouds in the Milky Way (Liszt & Lucas 1996) persists out to z ~ 1. It has been suggested (Liszt & Lucas 1999) that OH is a good tracer of H2, with NH2/NOH ≈ 107 under a variety of physical conditions. We use this relationship to estimate NH2 in these absorbers. The estimated NH2 is ≳ 1022 in all four cases and substantially different from estimates based on CO observations.

Item Type:Article
Source:Copyright of this article belongs to EDP Sciences.
Keywords:Galaxies: Evolution; Galaxies: Formation; Galaxies: ISM; Cosmology: Observations; Radio Lines: Galaxies
ID Code:63526
Deposited On:29 Sep 2011 04:05
Last Modified:29 Sep 2011 04:05

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