Gamma-ray line emission from OB associations and young open clusters. II. The Cygnus region

Abstract

Gamma-ray and microwave observations of the Cygnus region reveal an intense signal of 1.809 MeV line emission, attributed to radioactive decay of 26Al, that is closely correlated with 53 GHz free-free emission, originating from the ionised interstellar medium. We modelled both emissions using a multi-wavelength evolutionary synthesis code for massive star associations that we applied to the known massive star populations in Cygnus. For all OB associations and young open clusters in the field, we determined the population age, distance, and richness as well as the uncertainties in all these quantities from published photometric and spectroscopic data. We propagate the population uncertainties in model uncertainties by means of a Bayesian method. The young globular cluster Cyg OB2 turns out to be the dominant 26Al nucleosynthesis and ionisation source in Cygnus. Our model reproduces the ionising luminosity of the Cygnus region very well, yet it underestimates 26Al production by about a factor of 2. We attribute this underestimation to shortcomings of current nucleosynthesis models, and suggest the inclusion of stellar rotation as possible mechanism to enhance 26Al production. We also modelled 60Fe nucleosynthesis in the Cygnus region, yet the small number of recent supernova events suggests only little 60Fe production. Consequently, a detection of the 1.137 MeV and 1.332 MeV decay lines of 60Fe from Cygnus by the upcoming INTEGRAL observatory is not expected.

24 pages, 7 figures, accepted for publication in A&A

References in corpus (5)

• Stellar evolution with rotation VII: Low metallicity models and the blue to red supergiant ratio in the SMC
• On the effective temperature scale of O stars
• New infrared star clusters and candidates in the Galaxy detected with 2MASS
• Effect of Dust Extinction on Estimating Star Formation Rate of Galaxies: Lyman Continuum Extinction
• Near Infrared Observations of the Giant HII Region W49A: A Starbirth Cluster

Cited by in corpus (35)

• Ten Million Degree Gas in M 17 and the Rosette Nebula: X-ray Flows in Galactic H II Regions
• The Galactic WC stars: Stellar parameters from spectral analyses indicate a new evolutionary sequence
• A Study of Cyg OB2: Pointing the Way Towards Finding Our Galaxy's Super Star Clusters
• SPI observations of the diffuse 60Fe emission in the Galaxy
• Cosmic ray neon, Wolf-Rayet stars, and the superbubble origin of galactic cosmic rays
• HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
• Probing Planck scale physics with IceCube
• On the shape of the spectrum of cosmic-rays accelerated inside superbubbles
• New estimates of the contribution of Wolf--Rayet stellar winds to the Galactic 26Al
• Radioactive 26Al from the Scorpius-Centaurus Association
• Nuclear-Astrophysics Lessons from INTEGRAL
• Unveiling the Cygnus OB2 stellar population with Chandra
• Detection of gamma-ray lines from interstellar 60Fe by the high resolution spectrometer SPI
• The production of short-lived radionuclides by new non-rotating and rotating Wolf-Rayet model stars
• On the recent star formation history of the Milky Way disk
• TeV gamma-rays and neutrinos from photo-disintegration of nuclei in Cygnus OB2
• Feedback by massive stars and the emergence of superbubbles II. X-ray properties
• Hyperfast pulsars as the remnants of massive stars ejected from young star clusters
• A spectroscopic investigation of the O-type star population in four Cygnus OB associations. I. Determination of the binary fraction
• New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations
• X-ray and Radio Observations of the gamma Cygni Supernova Remnant G78.2+2.1
• The stochastic nature of stellar population modelling
• Discovery of a WO star in the Scutum-Crux arm of the inner Galaxy
• Predicted gamma-ray line emission from the Cygnus complex
• Steady-state nucleosynthesis throughout the Galaxy
• 26Al yields from rotating Wolf--Rayet star models
• Separated before birth: pulsars B2020+28 and B2021+51 as the remnants of runaway stars
• Very massive star winds as sources of the short-lived radioactive isotope ${}^{26}$Al
• 3D numerical model of the Omega Nebula (M17): simulated thermal X-ray emission
• The Galactic 26Al Problem and The Close Binary SNIb/c Solution?
• Present and Future Gamma-Ray Probes of the Cygnus OB2 Environment
• Cosmic Radioactivity and Galactic Chemical Evolution
• Investigation of the double-lobed sources of the Cygnus constellation core
• Deciphering the gamma-ray emission in the Cygnus region
• Oxygen and silicon abundances in Cygnus OB2: Chemical homogeneity in a sample of OB slow rotators