Space distribution of IRAS sources: Difference between oxygen-rich and carbon stars

National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan

Corresponding author: K. Noguchi, knoguchi@optik.mtk.nao.ac.jp

Received: 5 February 1998
Accepted: 14 January 2004

Abstract

We have examined the space distribution of IRAS sources in the Galaxy paying attention in particular to the difference between oxygen-rich and carbon stars. The sample consists of about 70 000 sources with good quality photometric data both at 12 and 25 μm. Sample sources are mostly post main sequence stars. Oxygen-rich asymptotic giant branch stars show the highest stellar density at the Galactic center. The density decreases with the increase in the Galactocentric distance. On the other hand, carbon stars show a uniform density distribution within about 3.6 kpc of the Sun. Thus the ratio of carbon stars to oxygen-rich asymptotic giant branch stars increases with the increase in the Galactocentric distance within the range between about 5 and 12 kpc.