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Session 70 - The Milky Way.
Display session, Wednesday, January 15
Metropolitan Ballroom,
Using the 12 micron absolute magnitude and the [12]-[25] color index relationship for Supergiants and Mira variables by Hickman et al (1996), the distribution of suspected evolved IR variable stars was investigated. Point source candidates were chosen via colors from the IRAS Point Source Catalog (version 2) within the following ranges: all candidates: -0.40 < [12]-[25] < 1.50; Supergiants: -0.22 < [25]-[60] < 0.65; Mira variables: -0.52 < [25]-[60] < 0.10. All point sources candidates had an IRAS variability index greater than 0.90 and high flux quality in all 12, 25, and 60 micron bands. Using the Hickman et al relationship for sources with known distance moduli, we calculate an average error of 25the distance determination. This error is consistent with the scatter in the original data by Hickman et al mostly due to poorly known distances. We then applied the Hickman et al relationship to our larger sample of IRAS variable sources (a total of 1395) to obtain their distribution in the Galaxy. Statistical tests were then used to look for evidence of the galactic center and spiral arms. These tests focused on the Supergiants since they are younger than the Mira variables and thus showed more evidence of galactic structure.
