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Issue A&A Volume 430, Number 2, February I 2005 Page(s) 561 - 566 Section Interstellar and circumstellar matter DOI 10.1051/0004-6361:20041220

A&A 430, 561-566 (2005)
DOI: 10.1051/0004-6361:20041220

An alternate estimate of the mass of dust in Cassiopeia A

T. L. Wilson^{1, 2} and W. Batrla<sup>2

1</sup>  European Southern Observatory, K-Schwarzschild-Strasse 2, 85748 Garching, Germany
    e-mail: twilson@eso.org
²  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

(Received 3 May 2004 / Accepted 28 September 2004 )

Abstract
Recent observations of sub-millimeter continuum emission toward supernova remnants (SNR) have raised the question of whether such emission is caused by dust within the SNR itself or along the line-of-sight. Here we make a comparison of the image of sub-mm emission from dust with the integrated J=1-0 line emission from interstellar toward the SNR Cassiopeia A based on existing data. The cm and mm synchrotron emission from Cas A has a rather symmetric, ring-like structure whereas both the sub-mm continuum and interstellar line emission are located mostly toward the south of the SNR. There is positional agreement for 3 of 6 maxima found in line and sub-mm continuum emission, with the weakest feature near the center of Cas A and the other two features near the southeast and west edges of the SNR. For these three maxima, a comparison of masses determined from dust and data shows good agreement if we use the 450  m dust absorption coefficient typical for diffuse clouds. There is also good agreement between the sub-mm dust temperature and the gas kinetic temperature from CO and . For the remaining sub-mm continuum peaks, one is outside the forward shock of the SNR. For the other two, one was not mapped in ¹³CO; for the other there is no ¹³CO emission. absorption covers all of Cas A, but the column density may be too small to account for the sub-mm dust emission. Thus it is possible that one, or perhaps two of these sub-mm continuum peaks are located inside the SNR. From lower resolution maps in CO lines, the SE and W features are the edges of extended clouds. Toward the cloud centers, the CO emission is more intense, but there appears to be less sub-mm dust emission. The differences between CO and sub-mm images may be caused a combination of the techniques used to produce the sub-mm maps and changes in cloud properties from center to edge.

Key words: stars: supernovae: individual: Cassiopia A -- submillimeter -- radio lines: ISM -- galaxies: abundances -- ISM: dust, extinction

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© ESO 2005

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