Letter to the Editor

A Herschel PACS and SPIRE study of the dust content of the Cassiopeia A supernova remnant ^*,**

¹ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK e-mail: mjb@star.ucl.ac.uk
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³ Space Science and Technology Department, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
⁴ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
⁵ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
⁶ School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, Wales CF24 3AA, UK
⁷ Dept of Astronomy, Stockholm University, AlbaNova University Center, Roslagstulsbacken 21, 10691 Stockholm, Sweden
⁸ Institute for Space Imaging Science, University of Lethbridge, Lethbridge, Alberta, TJ1 1B1, Canada

Received: 30 March 2010
Accepted: 12 May 2010

Abstract

Using the 3.5-m Herschel Space Observatory, imaging photometry of Cas A has been obtained in six bands between 70 and 500 μm with the PACS and SPIRE instruments, with angular resolutions ranging from 6 to 37”. In the outer regions of the remnant the 70-μm PACS image resembles the 24-μm image Spitzer image, with the emission attributed to the same warm dust component, located in the reverse shock region. At longer wavelengths, the three SPIRE bands are increasingly dominated by emission from cold interstellar dust knots and filaments, particularly across the central, western and southern parts of the remnant. Nonthermal emission from the northern part of the remnant becomes prominent at 500 μm. We have estimated and subtracted the contributions from the nonthermal, warm dust and cold interstellar dust components. We confirm and resolve for the first time a cool (~35 K) dust component, emitting at 70-160 μm, that is located interior to the reverse shock region, with an estimated mass of 0.075 .