WSRT HI synthesis absorption study towards Cassiopeia A

¹ Kapteyn Astronomical Institute, Groningen University, Postbus 800, 9700 AV Groningen, The Netherlands
² National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, U.S.A.
³ Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn 1, Germany

Send offprint request to: U.J. Schwarz

Received: 23 May 1996
Accepted: 28 August 1996

Abstract

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 s^-1. In previous studies, observations are described either with lower velocity resolution or with a limited velocity range (below -30 km s^-1), 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 s^-1. At a velocity of -1.5 km s^-1 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 ¹³CO feature observed by Wilson et al. (1993). Based on the new HI absorption results we derive the ratio .