Observations of Galaxies with the Midcourse Space Experiment

We have imaged eight nearby spiral galaxies with the SPIRIT III infrared telescope on the Midcourse Space Experiment (MSX) satellite in the mid-infrared at 18" resolution at 8.3, 12.1, 14.7, and 21.3 μm. Each of the eight shows interesting structure not previously detected with older, lower resolution infrared data sets, such as a resolved nucleus or spiral structure. The MSX data are compared with existing data sets at ultraviolet, optical, and infrared wavelengths, including recent observations from the Infrared Space Observatory. The infrared structures in M83 and NGC 5055 show a striking similarity to the ultraviolet emission but are less similar to the optical emission. Several point sources with no identified counterparts at other wavelengths are found near M31, NGC 4945, M83, and M101. Over 200 previously known objects are also detected at 8 μm.