Chemical evolution of 26Al and 60Fe in the Milky Way

We present theoretical mass estimates of Al-26 and Fe-60 throughout the Galaxy, performed with a numerical chemical evolution model including detailed nucleosynthesis prescriptions for stable and radioactive nuclides. We compared the results for several sets of stellar yields taken from the literature, for massive, low and intermediate mass stars, nova systems (only for Al-26) and supernovae Type Ia. We then computed the total masses of Al-26 and Fe-60 in the Galaxy. We studied the bulge and the disc of the Galaxy in a Galactocentric radius range of 0-22 kpc. We assumed that the bulge region (within 2 kpc) evolved quickly suffering a strong star formation burst, while the disc formed more slowly and inside-out. We compared our results with the Al-26 mass observed by the gamma-ray surveys COMPTEL and INTEGRAL to select the best model. Concerning Fe-60, we do not have any observed mass value so we just performed a theoretical prediction for future observations. In conclusion, low, intermediate mass stars, and Type Ia supernovae contribute negligibly to the two isotopes, while massive stars are the dominant source. The nova contribution is, however, necessary to reproduce the observations of Al-26. Our best model predicts 2.12 M-circle dot of Al-26, in agreement with observations, while for Fe-60 our best mass estimate is similar to 1.05 M-circle dot. We also predicted the present injection rate of Al-26 and Fe-60 in the Galaxy and compared it with previous results, and we found a larger present time injection rate along the disc.

Automated summary

We present theoretical mass estimates of Al-26 and Fe-60 throughout the Galaxy using a numerical chemical evolution model. We compared different sets of stellar yields and found that massive stars are the dominant source for these isotopes, while low and intermediate mass stars and Type Ia supernovae contribute negligibly. The contribution of nova systems is necessary to reproduce the observations of Al-26. Our best model predicts a mass of 2.12 solar masses for Al-26, in agreement with observations, and a mass estimate of around 1.05 solar masses for Fe-60.