Galactic Population Synthesis of Radioactive Nucleosynthesis Ejecta

Abstract

Diffuse gamma-ray line emission traces freshly produced radioisotopes in the interstellar gas, providing a unique perspective on the entire Galactic cycle of matter from nucleosynthesis in massive stars to their ejection and mixing in the interstellar medium. We aim at constructing a model of nucleosynthesis ejecta on galactic scale which is specifically tailored to complement the physically most important and empirically accessible features of gamma-ray measurements in the MeV range, in particular for decay gamma-rays such as ${}^{26}$Al, ${}^{60}$Fe or ${}^{44}$Ti. Based on properties of massive star groups, we developed a Population Synthesis Code which can instantiate galaxy models quickly and based on many different parameter configurations, such as the star formation rate, density profiles, or stellar evolution models. As a result, we obtain model maps of nucleosynthesis ejecta in the Galaxy which incorporate the population synthesis calculations of individual massive star groups. Based on a variety of stellar evolution models, supernova explodabilities, and density distributions, we find that the measured ${}^{26}$Al distribution from INTEGRAL/SPI can be explained by a Galaxy-wide population synthesis model with a star formation rate of $4$-$8{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ and a spiral-arm dominated density profile with a scale height of at least 700 pc. Our model requires that most massive stars indeed undergo a supernova explosion. This corresponds to a supernova rate in the Milky Way of $1.8$-$2.8$ per century, with quasi-persistent ${}^{26}$Al and ${}^{60}$Fe masses of $1.2$-$2.4{\mathrm{M}}_{\odot }$ and $1$-$6{\mathrm{M}}_{\odot }$, respectively. Comparing the simulated morphologies to SPI data suggests that a frequent merging of superbubbles may take place in the Galaxy, and that an unknown but strong foreground emission at 1.8 MeV could be present.

16 pages, 12 figures, 2 page appendix, accepted for publication in A&A

References in corpus (25)

• Binary interaction dominates the evolution of massive stars
• Nucleosynthesis and Remnants in Massive Stars of Solar Metallicity
• The nucleosynthesis of Al26 and Fe60 in solar metallicity stars extending in mass from 11 to 120 Msun: the hydrostatic and explosive contributions
• Detection of large-scale X-ray bubbles in the Milky Way halo
• A Superbubble Feedback Model for Galaxy Simulations
• Cooling, Gravity and Geometry: Flow-driven Massive Core Formation
• The distribution of the ISM in the Milky Way A three-dimensional large-scale model
• Converting H$\alpha$ Luminosities into Star Formation Rates
• The optimally-sampled galaxy-wide stellar initial mass function - Observational tests and the publicly available GalIMF code
• Fermi and eRosita bubbles as relics of the past activity of the Galactic black hole
• The Galactic ${}^{26}$Al emission map as revealed by INTEGRAL/SPI
• Feedback by massive stars and the emergence of superbubbles II. X-ray properties
• 26Al kinematics: superbubbles following the spiral arms? Constraints from the statistics of star clusters and HI supershells
• Gamma-ray Emission of 60Fe and 26Al Radioactivities in our Galaxy
• Prestellar Core Formation, Evolution, and Accretion from Gravitational Fragmentation in Turbulent Converging Flows
• Biases on initial mass function determinations. II. Real multiple systems and chance superpositions
• ${}^{60}$Fe in core-collapse supernovae and prospects for X-ray and $\gamma$-ray detection in supernova remnants
• Dynamics and Energy Loss in Superbubbles
• Background modelling for $\gamma$-ray spectroscopy with INTEGRAL/SPI
• Comparing simulated ${}^{26}$Al maps to gamma-ray measurements
• Galactic 26Al traces metal loss through hot chimneys
• Synthetic ${}^{26}$Al emission from galactic-scale superbubble simulations
• Distribution and kinematics of 26Al in the Galactic disc
• Vertical position of the Sun with $\gamma$-rays
• Popsynth: A generic astrophysical population synthesis framework