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A&A Supplement series, Vol. 123, May II 1997, 43-58

Received May 23; accepted August 28, 1996

WSRT HI synthesis absorption study towards Cassiopeia A

U.J. Schwarztex2html_wrap1432 - W.M. Gosstex2html_wrap1434 - P.M.W. Kalberlatex2html_wrap1436

Send offprint request: U.J. Schwarz

tex2html_wrap1438  Kapteyn Astronomical Institute, Groningen University, Postbus 800, 9700 AV Groningen, The Netherlands
tex2html_wrap1440  National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, U.S.A.
tex2html_wrap1442  Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn 1, Germany


We present high resolution images of the entire galactic HI spectrum of Cas A and display the whole data cube in various ways; the spatial resolution is 30 arcsec and the velocity resolution is 0.62 km stex2html_wrap_inline1402. In previous studies, observations are described either with lower velocity resolution or with a limited velocity range (below -30 km stex2html_wrap_inline1406), (Bieging et al. 1991; Reynoso et al. 1997). Here we concentrate the discussion on the local HI gas, with velocities between -10 and +10 km stex2html_wrap_inline1412. At a velocity of -1.5 km stex2html_wrap_inline1416 we find a cold HI feature with a kinetic temperature of typically 25 K, with a small region of 1 by 2 arcmin with a kinetic temperature below 10 K. This feature can be associated with a tex2html_wrap_inline1418CO feature observed by Wilson et al. (1993). Based on the new HI absorption results we derive the ratio tex2html_wrap_inline1420.

keywords: ISM: Cas; clouds atoms -- radio lines: ISM

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