The Spatial Distribution of the Far‐Infrared Emission in NGC 253

We study the far-infrared emission properties of the nearby starburst galaxyNGC 253 based on IRAS maps and an ISOPHOT map at 180 microns. Based on theanalysis of the light profiles, we have been able to identify three mainstructural components: an unresolved nuclear component, an exponential disk,and a kiloparsec scale bar.In addition, we also found a ring structure at theend of the bar that is particularly conspicuous at 12 microns. The SpectralEnergy Distribution (SED) of each morphological component has been modeled asthermal dust emission at different temperatures. The unresolved nuclearcomponent is dominated by cold dust emission (T ~ 50 K), whereas the diskemission is dominated by very cold dust (T ~ 16 K) plus a contribution fromcold dust (T ~ 55 K). The bar emission corresponds mainly to cold dust (T ~ 23K) plus a warm component (T ~ 148 K). We detect an extension of the diskemission due to very cold dust, which contributes a large fraction (94%) of thetotal dust mass of the galaxy. The estimated total dust mass is 8.2 +/- 10^7Msun.Comment: 20 pages, 9 figures. Accepted in Ap