Star Formation in an Unexpected Place: Early-type Galaxies

Many early-type galaxies are detected at 24 to 160μm but the emission is usually dominated by an AGN or heating from the evolved stellar population. Here we present MIPS observations of a sample of elliptical and lenticular galaxies which are rich in cold molecular gas, and we investigate how much of the MIR to FIR emission could be due to star formation activity. The 24μm images show a rich variety of structures, including nuclear point sources, rings, disks, and smooth extended emission, and comparisons to matched-resolution CO and radio continuum images suggest that the bulk of the 24μm emission could be traced to star formation. The star formation efficiencies are comparable to those found in normal spirals. Some future directions for progress are also mentioned. Subject headings: galaxies: ISM — infrared: galaxies — infrared: ISM — ISM: dust, extinction — ISM: structure — galaxies: elliptical and lenticular, cD