Title: Evidence for Unresolved $\gamma$ -Ray Point Sources in the Inner Galaxy

Abstract

We propose a new method to characterize unresolved point sources (PSs) generalizing traditional template fits to account for non-Poissonian photon statistics. We apply this method to Fermi Large Area Telescope γ-ray data to characterize PS populations at high latitudes and in the Inner Galaxy. We discover that PSs (resolved and unresolved) account for ~50% of the total extragalactic γ-ray background in the energy range ~1.9 to 11.9 GeV.Within 10° of the Galactic Center with |b| ≥ 2°, we find that ~5%–10% of the flux can be accounted for by a population of unresolved PSs distributed consistently with the observed ~GeV γ-ray excess in this region. The excess is fully absorbed by such a population, in preference to dark-matter annihilation. The inferred source population is dominated by near-threshold sources, which may be detectable in future searches.

Authors:

Lee, Samuel K. ^[1]; Lisanti, Mariangela ^[2]; Safdi, Benjamin R. ^[3]; Slatyer, Tracy R. ^[3]; Xue, Wei ^[3]

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+ Show Author Affiliations

1. Princeton Univ., Princeton, NJ (United States); Broad Inst., Cambridge, MA (United States)
2. Princeton Univ., Princeton, NJ (United States)
3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Publication Date:

2016-02-04

Research Org.:

Princeton Univ., NJ (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)

OSTI Identifier:

1505726

Alternate Identifier(s):

OSTI ID: 1236973

Grant/Contract Number:  

SC0007968; SC00012567; SC0013999

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review Letters

Additional Journal Information:

Journal Volume: 116; Journal Issue: 5; Journal ID: ISSN 0031-9007

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS