Weighting the Mass of NGC 253: Mid and Far Infrared Spatial Distribution

Abstract

The real dimensions of a spiral galaxy are crucial to understand the impact of intense star formation in the galaxy and to study the possibility that processed material be throw out to intergalactic medium. For this is necesary to map as many galactic components as be possible and in particular the spatial distribution of cold material, e.g. dust. In a recent paper (Melo et al. 2002) we have study the far-infrared emission properties of the nearby starburst galaxy NGC 253 based on IRAS maps and an ISOPHOT map at 180 µm. Based on the analysis of the light profiles, we have been able to identify three main structural components: an unresolved nuclear component, an exponential disk, and a kiloparsec scale bar. In addition, we also found a ring structure at the end of the bar that is particularly conspicuous at 12 µm. The Spectral Energy Distribution (SED) of each morphological component has been modeled as thermal dust emission at different temperatures. We detect an extension of the disk emission due to very cold dust, which contributes a large fraction (94%) of the total dust mass of the galaxy. The estimated total dust mass is 8.2 × 107 M⊙.