Cassiopeia A dust composition and heating

Abstract

Material ejected by a supernova is directly observed in the form of Fast Moving Knots (FMK's) in the Cassiopeia A supernova remnant. Part of this material has condensed into dust. In this paper, by fitting the ISO mid-infrared emission of the dust, we derive the dust composition and discuss the dust heating. The dust is found to be made mainly of three components: pyroxene, quartz and aluminium oxide. These components have to be heated at two different temperatures, a ``hot'' temperature around 350 K and a cold temperature around 90 K. The physical conditions in the knot-shocked region are such that the dust can be collisionally heated to a temperature of 350 K. The cold dust temperature can also be well accounted for by the knot model discussed in the paper. The dust formation efficiency is tentatively estimated to be of the order of 10% in this supernova. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA, and on observations obtained at Canada-France-Hawaii Telescope.