Document Type

Article

Publication Date

Spring 4-1-1995

Publication Title

The Astrophysical Journal

Publisher

The American Astronomical Society

Abstract

Using recently calcualted yields from Type II supernovae, along with models for chemical evolution and the distribution of mass in the interstellar medium, the current abundances and spatial distribution of mass in the interstellar medium, the current abundances and spatial distributions of two key gamma-ray radiactivites, 26Al and 60Fe, and determined. The estimated steady state production rates are 2.0±1.0 M☉ Myr^-1 for 26Al and 0.75±0.4 M☉ Myr^-1 for 60 Fe. This corresponds to 2.2±1.1 M☉ of 26Al and 1.7±0.9 M☉ of 60Fe in the present interstellar medium. Sources of uncertainty are discussed, one of the more important being the current rate of core collapse supernovae in the Galaxy. Our simple model gives three per century, but reasonable changes in the star formation rate could easily accommodate a core collapse rate one-half as large, and thus one-half the yeilds. When these stellar and chemical evolution results are mapped into a three dimensional model of the galaxy, the calculated 1809 keV gamma ray flux map is consistent with the Compton Gamm Ray Observatory observations of a steep decline in the flux outside longitude of ± 50° from the Galatic center, and the slight flux enhancements observed in the vicinity of spiral arms. Other potential stellar sourcs of 26Al and 60Fe are mentioned, especially the possibility of 60Fe synthesis in Type Ia supernovae. Predidtion for the 60Fe mass distribution, total mass, and flux map are given.

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