Cassiopeia A supernova remnant?

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 M. Key words. ISM: supernova remnants; (ISM): dust, extinction; Infrared: ISM 1