Title: Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies

Abstract

The Fermi-LAT Collaboration has studied the gamma-ray emission from a stacked population of dwarf spheroidal galaxies and used this information to set constraints on the dark matter annihilation cross section. Interestingly, their analysis uncovered an excess with a test statistic (TS) of 8.7. If interpreted naively, this constitutes a 2.95σ local excess (p-value=0.003), relative to the expectations of their background model. In order to further test this interpretation, the Fermi-LAT team studied a large number of blank sky locations and found TS>8.7 excesses to be more common than predicted by their background model, decreasing the significance of their dwarf excess to 2.2σ(p-value=0.027). We argue that these TS>8.7 blank sky locations are largely the result of unresolved blazars, radio galaxies, and star-forming galaxies, and show that multiwavelength information can be used to reduce the degree to which such sources contaminate the otherwise blank sky. In particular, we show that masking regions of the sky that lie within 1° of sources contained in the BZCAT or CRATES catalogs reduce the fraction of blank sky locations with TS>8.7 by more than a factor of 2. Taking such multiwavelength information into account can enable experiments such as Fermi to better characterize their backgrounds andmore » increase their sensitivity to dark matter in dwarf galaxies, the most important of which remain largely uncontaminated by unresolved point sources. We also note that for the range of dark matter masses and annihilation cross sections currently being tested by studies of dwarf spheroidal galaxies, simulations predict that Fermi should be able to detect a significant number of dark matter subhalos. These subhalos constitute a population of subthreshold gamma-ray point sources and represent an irreducible background for searches for dark matter annihilation in dwarf galaxies.« less

Authors:

Carlson, Eric ^[1]; Hooper, Dan ^[2]; Linden, Tim ^[3]

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+ Show Author Affiliations

1. Univ. of California, Santa Cruz, CA (United States). Dept. of Physics
2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States). Center for Particle Astrophysics; Univ. of Chicago, IL (United States). Dept. of Astronomy and Astrophysics
3. Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics

Publication Date:

2015-03-01

Research Org.:

Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

Sponsoring Org.:

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

OSTI Identifier:

1333173

Report Number(s):

FERMILAB-PUB-14-312-A; arXiv:1409.1572
Journal ID: ISSN 1550-7998; PRVDAQ; 1315275

Grant/Contract Number:  

AC02-07CH11359

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. D, Particles, Fields, Gravitation and Cosmology

Additional Journal Information:

Journal Volume: 91; Journal Issue: 6; Journal ID: ISSN 1550-7998

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS