Gamma-ray spectroscopy of galactic nucleosynthesis

Abstract

Diffuse gamma-ray emission from the decay of radioactive ${}^{26}$Al is a messenger from the nucleosynthesis activity in our current-day galaxy. Because this material is attributed to ejections from massive stars and their supernovae, the gamma-ray signal includes information about nucleosynthesis in massive star interiors as it varies with evolutionary stages, and about their feedback on the surrounding interstellar medium. Our method of population synthesis of massive-star groups has been refined as a diagnostic tool for this purpose. It allows to build a bottom-up prediction of the diffuse gamma-ray sky when known massive star group distributions and theoretical models of stellar evolution and core-collapse supernova explosions are employed. We find general consistency of an origin in such massive-star groups, in particular we also find support for the clumpy distribution of such source regions across the Galaxy, and characteristics of large cavities around these. A discrepancy in the integrated ${}^{26}$Al gamma-ray flux is interpreted as an indication for excess ${}^{26}$Al emission from nearby, distributed in cavities that extend over major regions of the sky.

arXiv comment6 pages, 2 figures. Invited contribution to conference 'Nuclear Physics in Astrophysics X', Geneva Sep 2022

References in corpus (12)

• Radioactive 26Al and massive stars in the Galaxy
• Birth and Evolution of Isolated Radio Pulsars
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• Revisiting the radial distribution of pulsars in the Galaxy
• SPI/INTEGRAL in-flight performance
• Kinematics of massive star ejecta in the Milky Way as traced by 26Al
• Using population synthesis of massive stars to study the interstellar medium near OB associations
• INTEGRAL/SPI $\gamma$-ray line spectroscopy
• 26Al kinematics: superbubbles following the spiral arms? Constraints from the statistics of star clusters and HI supershells
• Background modelling for $\gamma$-ray spectroscopy with INTEGRAL/SPI
• Comparing simulated ${}^{26}$Al maps to gamma-ray measurements
• Steady-state nucleosynthesis throughout the Galaxy