Mapping and Mass Measurement of the Cold Dust in NGC 205 with Spitzer

Abstract

We present observations at 3.6, 4.5, 5.8, 8, 24, 70, and 160 μm of NGC 205, the dwarf elliptical companion of M31, obtained with the Spitzer Space Telescope. The point-source-subtracted images at 8 and 24 μm display a complex and fragmented infrared emission coming from both very small dust particles and larger grains. The extended dust emission is spatially concentrated in three main emission regions, seen at all wavelengths from 8 to 160 μm. These regions lie approximately along NGC 205's semimajor axis and range from ~100 to 300 pc in size. On the basis of our mid-/far-infrared flux density measurements alone, we derive a total dust mass estimate on the order of 3.2×10 4 M solar, mainly at a temperature of ~20 K. The gas mass associated with this component matches the predicted mass returned by the dying stars from the last burst of star formation