Steady-state nucleosynthesis throughout the Galaxy

Abstract

Measurement and astrophysical interpretation of characteristic gamma-ray lines from nucleosynthesis was one of the prominent science goals of the INTEGRAL mission and in particular its spectrometer SPI. Emission from 26Al and from 60Fe decay lines originates from accumulated ejecta of nucleosynthesis sources, and appears diffuse in nature. 26Al and 60Fe are believed to originate mostly from massive star clusters. Gamma-ray observations open an interesting window to trace the fate and flow of nucleosynthesis ejecta, after they have left the immediate sources and their birth sites, and on their path to mix with ambient interstellar gas. The INTEGRAL 26Al emission image confirms earlier findings of clumpiness and an extent along the entire plane of the Galaxy, supporting its origin from massive-star groups. INTEGRAL spectroscopy resolved the line and found Doppler broadenings and systematic shifts from large-scale galactic rotation. But an excess velocity of ~200 km/s suggests that 26Al decays preferentially within large superbubbles that extend in forward directions between spiral arms. The detection of 26Al line emission from nearby Orion and the Eridanus superbubble supports this interpretation. Positrons from beta+ decays of 26Al and other nucleosynthesis ejecta have been found to not explain the morphology of positron annihilation gamma-rays at 511 keV that have been measured by INTEGRAL. The 60Fe signal measured by INTEGRAL is diffuse but too weak for an imaging interpretation, an origin from point-like/concentrated sources is excluded. The 60Fe/26Al ratio is constrained to a range 0.2-0.4. Beyond improving precision of these results, diffuse nucleosynthesis contributions from novae (through 22Na radioactivity) and from past neutron star mergers in our Galaxy (from r-process radioactivity) are exciting new prospects for the remaining mission extensions.

arXiv comment38 pages, 12 Figures. Contribution to Review Book "15 years of INTEGRAL". Accepted for publication in New Astronomy Reviews

References in corpus (47)

• Embedded Clusters in Molecular Clouds
• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Toward Understanding Massive Star Formation
• Physical Properties of Wolf-Rayet Stars
• Radioactive 26Al and massive stars in the Galaxy
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Nucleosynthesis in Classical Novae: ONe vs. CO White Dwarfs
• The nucleosynthesis of Al26 and Fe60 in solar metallicity stars extending in mass from 11 to 120 Msun: the hydrostatic and explosive contributions
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• Stellar Models and Yields of Asymptotic Giant Branch Stars
• The 511 keV emission from positron annihilation in the Galaxy
• Dawes Review 4: Spiral Structures in Disc Galaxies
• Nucleosynthesis of light elements inside thermally pulsing AGB stars I: the case of intermediate-mass stars
• Early SPI/INTEGRAL contraints on the morphology of the 511 keV line emission in the 4th galactic quadrant
• New limit of ${}^{244}$Pu on Earth points to rarity of actinide nucleosynthesis
• Gamma-ray spectroscopy of Positron Annihilation in the Milky Way
• 26Al and 60Fe From Supernova Explosions
• 3D dynamical evolution of the interstellar gas in the Gould Belt
• Signatures of a two million year old supernova in the spectra of cosmic ray protons, antiprotons and positrons
• Stellar feedback efficiencies: supernovae versus stellar winds
• Kinematics of massive star ejecta in the Milky Way as traced by 26Al
• Radioactive 26Al from the Scorpius-Centaurus Association
• Short-lived radioisotopes in meteorites from Galactic-scale correlated star formation
• Surround & Squash: The Interstellar Medium around Scorpius Centaurus OB2
• Using population synthesis of massive stars to study the interstellar medium near OB associations
• INTEGRAL/SPI $\gamma$-ray line spectroscopy
• The Galactic ${}^{26}$Al emission map as revealed by INTEGRAL/SPI
• Gamma-ray line emission from OB associations and young open clusters. II. The Cygnus region
• Dynamical Masses of Young Stars I: Discordant Model Ages of Upper Scorpius
• 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
• Probing the evolving massive star population in Orion with kinematic and radioactive tracers
• New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations
• Constraints from ${}^{26}$Al Measurements on the Galaxy's Recent Global Star Formation Rate and Core Collapse Supernovae Rate
• Triggered Star Formation on the Border of the Orion-Eridanus Superbubble
• Dynamics and Energy Loss in Superbubbles
• Superbubble evolution in disk galaxies, I. Study of blow-out by analytical models
• Comparing simulated ${}^{26}$Al maps to gamma-ray measurements
• Energetic feedback and ${}^{26}$Al from massive stars and their supernovae in the Carina region
• Predicted gamma-ray line emission from the Cygnus complex
• Nucleosynthesis of Fe60 in massive stars
• Synthetic ${}^{26}$Al emission from galactic-scale superbubble simulations
• Squeezed between shells? On the origin of the Lupus I molecular cloud. - II. APEX CO and GASS HI observations
• Cygnus OB2 - a young globular cluster in the Milky Way
• SPI/INTEGRAL observation of 1809 keV gamma-ray line emission from the Cygnus X region
• A New Look at Image Reconstruction of COMPTEL 1.8 MeV Data

Cited by in corpus (7)

• Measurement of Galactic ${}^{26}$Al with the Compton Spectrometer and Imager
• Gamma-Ray Light Curves and Spectra of Classical Novae
• Radioactive isotopes in the interstellar medium
• Cosmic Radioactivity and Galactic Chemical Evolution
• Nuclear astrophysics
• A New Versatile Code for Gamma-Ray Monte-Carlo Radiative Transfer
• Gamma-ray spectroscopy of galactic nucleosynthesis