A Population of Cold Cores in the Galactic Plane

Abstract

Recent observations by the Midcourse Space Experiment (MSX) have revealed the presence of compact objects seen in absorption against bright mid-infrared emission from the Galactic plane. Examination of MSX and IRAS images of these objects reveal that they are dark from 7 to 100 μm. We find ~2000 clouds in a 1° × 180° scan along the Galactic equator. The data suggest these objects are dense (n > 105 cm−3), cold (T<20 K) cores, without accompanying envelopes.