Highlight: Fermi/LAT observations of Local Group galaxies (vol. 523)

Vol. 523In section 1. Letters to the Editor10 November 2010

Fermi Large Area Telescope observations of Local Group galaxies: Detection of M31 and search for M33

by A. A. Abdo, M. Ackermann, M. Ajello, et al., A&A 523, L2 alt

Cosmic rays can be studied through the galaxy-wide gamma-ray emission above 100MeV that they generate when propagating in the interstellar medium. With the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope, the authors searched for gamma-ray emission from M31 and M33. For the first time, they have detected the gamma-ray luminosity from M31, which is half that of the Milky Way. They find no emission from M33. Comparing these to other Local Group galaxies and nearby starbursts, they find a good correlation between gamma-ray luminosity and star formation rate.