Predicted gamma-ray line emission from the Cygnus complex

Abstract

The Cygnus region harbours a huge complex of massive stars at a distance of 1.0-2.0kpc from us. About 170 O stars are distributed over several OB associations, among which the Cyg OB2 cluster is by far the most important with about 100-120 O stars. These massive stars inject large quantities of radioactive nuclei into the interstellar medium, such as 26Al and 60Fe, and their gamma-ray line decay signals can provide insight into the physics of massive stars and core-collapse supernovae. Past studies of the nucleosynthesis activity of Cygnus have concluded that the level of 26Al decay emission as deduced from CGRO/COMPTEL observations was a factor 2-3 above the predictions based on the theoretical yields available at that time and on the observed stellar content of the Cygnus region. We reevaluate the situation from new measurements of the gamma-ray decay fluxes with INTEGRAL/SPI and new predictions based on recently improved stellar models including some of the effects of stellar rotation for the higher mass stars and a coherent estimate of the contribution from SNIb/c. We developed a population synthesis code to predict the nucleosynthesis activity and corresponding decay fluxes of a given stellar population of massive stars. The observed decay fluxes from the Cygnus complex are found to be consistent with the values predicted by population synthesis at solar metallicity. The observed extent of the 1809keV emission from Cygnus is found to be consistent with the result of a numerical simulation of the diffusion of 26Al inside the superbubble blown by Cyg OB2. Our work indicates that the past dilemma regarding the gamma-ray line emission from Cygnus resulted from an overestimate of the 1809keV flux of the Cygnus complex, combined with an underestimate of the nucleosynthesis yields.

13 pages, 9 figures, accepted for publication in A&A

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Cited by in corpus (15)

• High-energy particles and radiation in star-forming regions
• Nuclear-Astrophysics Lessons from INTEGRAL
• Cosmic ray production in supernovae
• Electron-capture supernovae as sources of 60Fe
• Triggered Star Formation Inside the Shell of a Wolf-Rayet Bubble as the origin of the Solar System
• Feedback by massive stars and the emergence of superbubbles II. X-ray properties
• Energetic feedback and ${}^{26}$Al from massive stars and their supernovae in the Carina region
• Nuclear processes in Astrophysics: Recent progress
• Synthetic ${}^{26}$Al emission from galactic-scale superbubble simulations
• Steady-state nucleosynthesis throughout the Galaxy
• Galactic Population Synthesis of Radioactive Nucleosynthesis Ejecta
• Starbursts and High-Redshift Galaxies are Radioactive: High Abundances of ${}^{26}$Al and Other Short Lived Radionuclides
• The ${}^{26}$Al Gamma-ray Line from Massive-Star Regions
• Cosmic Radioactivity and Galactic Chemical Evolution
• Oxygen and silicon abundances in Cygnus OB2: Chemical homogeneity in a sample of OB slow rotators