D.A. Green,1 M.S. Clemens,2 P.
Alexander,1 H. Cullen1 and B.
Nikolic1
Abstract.
We present Giant Metrewave Radio Telescope 21-cm H I
observations
towards a sample of compact radio sources behind galaxy groups, to
search for cool
H I. The results from high dynamic range spectra for 8 lines-of-sight
through 7 galaxy
groups do not show any evidence for absorption by cool H I. At a
resolution of 20
km s-1 , the optical depth upper limits obtained were between 0.0075 and
0.035 (3 );
these correspond to upper limits of a few times 1023 m-2 for the column
density of any
cool H I along these lines of sight (assuming a spin temperature of 100
K).
Keywords: galaxies: clusters: general
intergalactic medium radio lines: galaxies
cosmology: miscellaneous
.
1 Mullard Radio Astronomy Observatory, Cavendish Laboratory, 19 J. J.
Thomson Avenue,
Cambridge CB3 0HE, United Kingdom
2 Dipartimento di Astronomia, Universita degli Studi di Padova, Vicolo
dell'Osservatorio, 2,
35122 Padova, Italy