The Spatial, Temporal, and Photometric Properties of AGB Stars

Abstract

The Two Micron Sky Survey (Neugebauer & Leighton 1969;TMSS) provides a census of AGB stars which is relatively insensitive to interstellar or circumstellar reddening, temporal variations, or differences in photospheric temperature. This paper summarizes results from recent analyses of all carbon, S type, and mass-losing M stars in the TMSS, including local surface densities, scale heights, and mass loss rates. All three groups are concentrated toward the plane; the mass-losing M stars appear least concentrated toward the plane but most strongly concentrated toward the galactic center. Results from the IRAS survey were used to determine the range of infrared colors of stars in each class, and to estimate their mass loss rates. Carbon stars have relatively higher 60 μm flux densities than oxygen-rich stars, and have relatively higher mass loss rates. The total mass loss rate is dominated by a small fraction of the stars in this sample. IRAS photometry and IRAS Low Resolution Spectometer data do not unambiguously distinguish carbon-rich and oxygen-rich stars in this sample. Future searches for stars with the greatest mass loss rates might concentrate on sources found to be variable in the IRAS survey, since a large fraction of the TMSS stars with the most massive envelopes are known Miras or infrared variables.