skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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:
 [1];  [2];  [3]
  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:
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:
Journal Article: 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

Citation Formats

Carlson, Eric, Hooper, Dan, and Linden, Tim. Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies. United States: N. p., 2015. Web. doi:10.1103/PhysRevD.91.061302.
Carlson, Eric, Hooper, Dan, & Linden, Tim. Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies. United States. https://doi.org/10.1103/PhysRevD.91.061302
Carlson, Eric, Hooper, Dan, and Linden, Tim. Sun . "Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies". United States. https://doi.org/10.1103/PhysRevD.91.061302. https://www.osti.gov/servlets/purl/1333173.
@article{osti_1333173,
title = {Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies},
author = {Carlson, Eric and Hooper, Dan and Linden, Tim},
abstractNote = {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 and 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.},
doi = {10.1103/PhysRevD.91.061302},
url = {https://www.osti.gov/biblio/1333173}, journal = {Physical Review. D, Particles, Fields, Gravitation and Cosmology},
issn = {1550-7998},
number = 6,
volume = 91,
place = {United States},
year = {2015},
month = {3}
}

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

Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Millisecond pulsars cannot account for the inner Galaxy’s GeV excess
journal, October 2013


THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION
journal, May 2009


Conservative constraints on dark matter from the Fermi-LAT isotropic diffuse gamma-ray background spectrum
journal, November 2010


The gamma-ray-flux PDF from galactic halo substructure
journal, July 2009


Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background
journal, November 2012


A brief introduction to PYTHIA 8.1
journal, June 2008


The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background
journal, August 2011


Clumps and streams in the local dark matter distribution
journal, August 2008


Dark matter and pulsar model constraints from Galactic Center Fermi-LAT gamma-ray observations
journal, October 2013


Two emission mechanisms in the Fermi Bubbles: A possible signal of annihilating dark matter
journal, September 2013


GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE
journal, August 2012


Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT
journal, April 2012


Dissecting the gamma-ray background in search of dark matter
journal, February 2014


FERMI LARGE AREA TELESCOPE SECOND SOURCE CATALOG
journal, March 2012


THE FERMI -LAT HIGH-LATITUDE SURVEY: SOURCE COUNT DISTRIBUTIONS AND THE ORIGIN OF THE EXTRAGALACTIC DIFFUSE BACKGROUND
journal, August 2010


Constraints on dark matter annihilation in clusters of galaxies with the Fermi large area telescope
journal, May 2010


CRATES: An All‐Sky Survey of Flat‐Spectrum Radio Sources
journal, July 2007

  • Healey, Stephen E.; Romani, Roger W.; Taylor, Gregory B.
  • The Astrophysical Journal Supplement Series, Vol. 171, Issue 1
  • https://doi.org/10.1086/513742

Astrophysical and dark matter interpretations of extended gamma-ray emission from the Galactic Center
journal, July 2014


Robust Identification of Isotropic Diffuse Gamma Rays from Galactic Dark Matter
journal, June 2009


Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope
journal, December 2011


SEARCH FOR DARK MATTER SATELLITES USING FERMI -LAT
journal, February 2012


Roma-BZCAT: a multifrequency catalogue of blazars
journal, December 2008


The Aquarius Project: the subhaloes of galactic haloes
journal, December 2008


Constraints on cosmological dark matter annihilation from the Fermi-LAT isotropic diffuse gamma-ray measurement
journal, April 2010


The flattening of the concentration–mass relation towards low halo masses and its implications for the annihilation signal boost
journal, June 2014


Contribution of blazars to the extragalactic diffuse gamma-ray background and their future spatial resolution
journal, November 2011


Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters
journal, December 2010


Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background
journal, September 2012


    Works referencing / citing this record:

    On The gamma-ray emission from Reticulum II and other dwarf galaxies
    journal, September 2015


    Wavelet-based techniques for the gamma-ray sky
    journal, July 2016


    A global analysis of dark matter signals from 27 dwarf spheroidal galaxies using 11 years of Fermi-LAT observations
    journal, February 2020


    Comprehensive search for dark matter annihilation in dwarf galaxies
    journal, April 2015


    Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II
    journal, August 2015


    SEARCHING FOR DARK MATTER ANNIHILATION IN RECENTLY DISCOVERED MILKY WAY SATELLITES WITH FERMI -LAT
    journal, January 2017


    ESTIMATING THE GeV EMISSION OF MILLISECOND PULSARS IN DWARF SPHEROIDAL GALAXIES
    journal, November 2016