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Title: Evidence for Unresolved γ -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:
 [1];  [2];  [3]; ORCiD logo [3];  [3]
  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:
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)
OSTI Identifier:
1505726
Alternate Identifier(s):
OSTI ID: 1236973
Report Number(s):
MIT-CTP-4684
Journal ID: ISSN 0031-9007; PRLTAO; SC0013999
Grant/Contract Number:  
SC0007968; SC0013999; SC0012567; PHY-1066293
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; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Lee, Samuel K., Lisanti, Mariangela, Safdi, Benjamin R., Slatyer, Tracy R., and Xue, Wei. Evidence for Unresolved γ -Ray Point Sources in the Inner Galaxy. United States: N. p., 2016. Web. doi:10.1103/physrevlett.116.051103.
Lee, Samuel K., Lisanti, Mariangela, Safdi, Benjamin R., Slatyer, Tracy R., & Xue, Wei. Evidence for Unresolved γ -Ray Point Sources in the Inner Galaxy. United States. doi:10.1103/physrevlett.116.051103.
Lee, Samuel K., Lisanti, Mariangela, Safdi, Benjamin R., Slatyer, Tracy R., and Xue, Wei. Thu . "Evidence for Unresolved γ -Ray Point Sources in the Inner Galaxy". United States. doi:10.1103/physrevlett.116.051103. https://www.osti.gov/servlets/purl/1505726.
@article{osti_1505726,
title = {Evidence for Unresolved γ -Ray Point Sources in the Inner Galaxy},
author = {Lee, Samuel K. and Lisanti, Mariangela and Safdi, Benjamin R. and Slatyer, Tracy R. and Xue, Wei},
abstractNote = {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.},
doi = {10.1103/physrevlett.116.051103},
journal = {Physical Review Letters},
number = 5,
volume = 116,
place = {United States},
year = {2016},
month = {2}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 88 works
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Figures / Tables:

FIG. 1. FIG. 1. : The source-count function for high-latitude point sources derived from applying non-Poissonian template fits to data with third Fermi-LAT catalog (3FGL) sources [42] unmasked (green band) and masked (orange band). The colored bands indicate 68% confidence intervals, which are computed pointwise in F from the posteriors for themore » source-count-function parameters, while the solid and dashed black lines show the median source-count functions. The black points show the source-count function of the detected point sources in the 3FGL. The vertical error bars indicate 68% confidence intervals; the horizontal bars denote bins in F.« less

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