A Study of M31, M87, NGC 253, and M82 in High-Energy Gamma Rays
Abstract
The data from the Energetic Gamma Ray Experiment Telescope (EGRET) all-sky survey are examined for emission from the nearby galaxies M31, M87, NGC 253, and M82 in the high-energy (E > 30 MeV) gamma-ray range. No significant emission is observed from any of these galaxies. The derived upper limits for all four galaxies are consistent with that expected from cosmic-ray interactions. For M87, the combination of the high-energy gamma-ray and radio data point to a lower limit of 7 microG for the magnetic field in the disk and 4 microG for the magnetic field in the halo, consistent with equipartition arguments. A study of NGC 253 and M82 show that EGRET observations do not sufficiently constrain the mean cosmic-ray energy density to provide more details on the cosmic-ray distribution in starburst galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1994
- DOI:
- 10.1086/174044
- Bibcode:
- 1994ApJ...426..105S
- Keywords:
-
- Cosmic Rays;
- Galaxies;
- Gamma Ray Astronomy;
- Interstellar Magnetic Fields;
- Magellanic Clouds;
- Sky Surveys (Astronomy);
- Gamma Ray Observatory;
- Gamma Ray Telescopes;
- Satellite-Borne Instruments;
- Sodium Iodides;
- Astronomy;
- ISM: COSMIC RAYS;
- GALAXIES: GENERAL;
- GAMMA RAYS: OBSERVATIONS