γ-Ray emission from Arp 220: indications of an active galactic nucleus
Journal article, 2017
Extragalactic cosmic ray populations are important diagnostic tools for tracking the distribution of energy in nuclei and for distinguishing between activity powered by star formation versus active galactic nuclei (AGNs). Here, we compare different diagnostics of the cosmic ray populations of the nuclei of Arp 220 based on radio synchrotron observations and the recent gamma-ray detection. We find the gamma-ray and radio emission to be incompatible; a joint solution requires at minimum a factor of 4-8 times more energy coming from supernovae and a factor of 40-70 more mass in molecular gas than that is observed. We conclude that this excess of the gamma-ray flux in comparison to all other diagnostics of star-forming activity indicates that there is an AGN present that is providing the extra cosmic rays, likely in the western nucleus.
gamma rays: galaxies
Supermassive Black-Holes
Continuum
galaxies: star-burst
galaxies: active
Galaxies
Array
cosmic rays
Coevolution
galaxies: individual: (Arp 220)
Resolution
Fermi-Lat
Arp-220
Author
T. M. Yoast-Hull
Canadian Institute for Theoretical Astrophysics
J. S. Gallagher III
University of Wisconsin Madison
Susanne Aalto
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Eskil Varenius
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 469 1 L89-L93Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1093/mnrasl/slx054