Kinematics of massive star ejecta in the Milky Way as traced by 26Al (K. Kretschmer et al.)

Vol. 559
In section 5. Galactic structure

Kinematics of massive star ejecta in the Milky Way as traced by 26Al

The presence of the short-lived isotope 26Al has been known through its decay line at 1.808 MeV ever since it was mapped by COMPTEL in the 1990s. The isotope is produced by massive stars in late stages of nucleosynthesis, especially by Wolf-Rayet and core collapse supernovae. This paper presents a remarkably comprehensive dynamical study of the Galactic distribution of this isotope using INTEGRAL spectroscopy. The scale height of the isotope was already known to be greater than for the likely Galactic sources, but this study also shows that its velocity is systematically greater than accounted for by Galactic differential rotation. Using the isotope as a tracer of the medium, the authors propose that this is due to the expulsion of gas in superbubbles from regions of star formation concentrated along the spiral arms in the inner Galaxy. The observed bias in the radial velocities is explained as blow-out from the leading edge of the arms into the inter-arm region, and from there into the halo.