COMPONENTS OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

Journal Article · Wed Jul 20 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/1/40· OSTI ID:21578321

Stecker, Floyd W ^[1]

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1. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

We present new theoretical estimates of the relative contributions of unresolved blazars and star-forming galaxies to the extragalactic {gamma}-ray background (EGB) and discuss constraints on the contributions from alternative mechanisms such as dark matter annihilation and truly diffuse {gamma}-ray production. We find that the Fermi source count data do not rule out a scenario in which the EGB is dominated by emission from unresolved blazars, though unresolved star-forming galaxies may also contribute significantly to the background, within order-of-magnitude uncertainties. In addition, we find that the spectrum of the unresolved star-forming galaxy contribution cannot explain the EGB spectrum found by EGRET at energies between 50 and 200 MeV, whereas the spectrum of unresolved flat spectrum radio quasars, when accounting for the energy-dependent effects of source confusion, could be consistent with the combined spectrum of the low-energy EGRET EGB measurements and the Fermi-Large Area Telescope EGB measurements.

• OSTI ID: 21578321
• Journal Information: Astrophysical Journal, Vol. 736, Issue 1; Other Information: DOI: 10.1088/0004-637X/736/1/40; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BACKGROUND RADIATION
COSMIC PHOTONS
GALAXIES
BOSONS
COSMIC RADIATION
ELEMENTARY PARTICLES
IONIZING RADIATIONS
MASSLESS PARTICLES
PHOTONS
RADIATIONS