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gamma-Ray emission from Arp 220: indications of an active galactic nucleus

T. M. Yoast-Hull ; J. S. Gallagher ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; Eskil Varenius (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium)
Monthly Notices of the Royal Astronomical Society (0035-8711). Vol. 469 (2017), 1, p. L89-L93.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: cosmic rays, galaxies: active, galaxies: individual: (Arp 220), galaxies: star-burst, gamma rays: galaxies, Supermassive Black-Holes, Fermi-Lat, Galaxies, Arp-220, Resolution, Coevolution, Continuum, Array

Denna post skapades 2017-09-26. Senast ändrad 2017-11-27.
CPL Pubid: 252074


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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium (2010-2017)


Astronomi, astrofysik och kosmologi

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