A Spitzer view of star formation in early-type galaxies

TL;DR

This study uses Spitzer MIPS observations to analyze star formation in early-type galaxies rich in molecular gas, revealing that much of their infrared emission is due to star formation with efficiencies similar to spiral galaxies.

Contribution

It demonstrates that star formation significantly contributes to IR emission in early-type galaxies, challenging the view that such emission is mainly from AGN or old stars.

Findings

24 micron emission correlates with star formation regions

Star formation efficiencies are comparable to spiral galaxies

Infrared emission is largely due to star formation activity

Abstract

Many early-type galaxies are detected at 24 to 160 micron 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 24 micron 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 24 micron emission can 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.