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

Title: A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER

Abstract

We present deep radio observations of four nearby dwarf spheroidal (dSph) galaxies, designed to detect extended synchrotron emission resulting from weakly interacting massive particle (WIMP) dark matter annihilations in their halos. Models by Colafrancesco et al. (CPU07) predict the existence of angularly large, smoothly distributed radio halos in such systems, which stem from electron and positron annihilation products spiraling in a turbulent magnetic field. We map a total of 40.5 deg{sup 2} around the Draco, Ursa Major II, Coma Berenices, and Willman 1 dSphs with the Green Bank Telescope (GBT) at 1.4 GHz to detect this annihilation signature, greatly reducing discrete-source confusion using the NVSS catalog. We achieve a sensitivity of {sigma}{sub sub} {approx}< 7 mJy beam{sup -1} in our discrete source-subtracted maps, implying that the NVSS is highly effective at removing background sources from GBT maps. For Draco we obtained approximately concurrent Very Large Array observations to quantify the variability of the discrete source background, and find it to have a negligible effect on our results. We construct radial surface brightness profiles from each of the subtracted maps, and jackknife the data to quantify the significance of the features therein. At the {approx}10' resolution of our observations, foregrounds contributemore » a standard deviation of 1.8 mJy beam{sup -1} {<=} {sigma}{sub ast} {<=} 5.7 mJy beam{sup -1} to our high-latitude maps, with the emission in Draco and Coma dominated by foregrounds. On the other hand, we find no significant emission in the Ursa Major II and Willman 1 fields, and explore the implications of non-detections in these fields for particle dark matter using the fiducial models of CPU07. For a WIMP mass M{sub {chi}} = 100 GeV annihilating into b b-bar final states and B = 1 {mu}G, upper limits on the annihilation cross-section for Ursa Major II and Willman I are log (({sigma}v){sub {chi}}, cm{sup 3} s{sup -1}) {approx}< -25 for the preferred set of charged particle propagation parameters adopted by CPU07; this is comparable to that inferred at {gamma}-ray energies from the two-year Fermi Large Area Telescope data. We discuss three avenues for improving the constraints on ({sigma}v){sub {chi}} presented here, and conclude that deep radio observations of dSphs are highly complementary to indirect WIMP searches at higher energies.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Department of Physics, Royal Military College of Canada, P.O. Box 17000, Station Forces, Kingston, Ontario K7K 7B4 (Canada)
  2. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)
  3. Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)
  4. Department of Astrophysical and Planetary Sciences, University of Colorado, 391 UCB, Boulder, CO 80309 (United States)
Publication Date:
OSTI Identifier:
22131061
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 773; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANNIHILATION; CATALOGS; CHARGED PARTICLES; CROSS SECTIONS; DWARF STARS; ELECTRONS; EMISSION; GALAXIES; GEV RANGE; GHZ RANGE; LIMITING VALUES; MAGNETIC FIELDS; NONLUMINOUS MATTER; POSITRONS; RADIOWAVE RADIATION; RESOLUTION; SENSITIVITY; SYNCHROTRON RADIATION; TELESCOPES

Citation Formats

Spekkens, Kristine, Mason, Brian S., Aguirre, James E., and Nhan, Bang. A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER. United States: N. p., 2013. Web. doi:10.1088/0004-637X/773/1/61.
Spekkens, Kristine, Mason, Brian S., Aguirre, James E., & Nhan, Bang. A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER. United States. https://doi.org/10.1088/0004-637X/773/1/61
Spekkens, Kristine, Mason, Brian S., Aguirre, James E., and Nhan, Bang. 2013. "A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER". United States. https://doi.org/10.1088/0004-637X/773/1/61.
@article{osti_22131061,
title = {A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER},
author = {Spekkens, Kristine and Mason, Brian S. and Aguirre, James E. and Nhan, Bang},
abstractNote = {We present deep radio observations of four nearby dwarf spheroidal (dSph) galaxies, designed to detect extended synchrotron emission resulting from weakly interacting massive particle (WIMP) dark matter annihilations in their halos. Models by Colafrancesco et al. (CPU07) predict the existence of angularly large, smoothly distributed radio halos in such systems, which stem from electron and positron annihilation products spiraling in a turbulent magnetic field. We map a total of 40.5 deg{sup 2} around the Draco, Ursa Major II, Coma Berenices, and Willman 1 dSphs with the Green Bank Telescope (GBT) at 1.4 GHz to detect this annihilation signature, greatly reducing discrete-source confusion using the NVSS catalog. We achieve a sensitivity of {sigma}{sub sub} {approx}< 7 mJy beam{sup -1} in our discrete source-subtracted maps, implying that the NVSS is highly effective at removing background sources from GBT maps. For Draco we obtained approximately concurrent Very Large Array observations to quantify the variability of the discrete source background, and find it to have a negligible effect on our results. We construct radial surface brightness profiles from each of the subtracted maps, and jackknife the data to quantify the significance of the features therein. At the {approx}10' resolution of our observations, foregrounds contribute a standard deviation of 1.8 mJy beam{sup -1} {<=} {sigma}{sub ast} {<=} 5.7 mJy beam{sup -1} to our high-latitude maps, with the emission in Draco and Coma dominated by foregrounds. On the other hand, we find no significant emission in the Ursa Major II and Willman 1 fields, and explore the implications of non-detections in these fields for particle dark matter using the fiducial models of CPU07. For a WIMP mass M{sub {chi}} = 100 GeV annihilating into b b-bar final states and B = 1 {mu}G, upper limits on the annihilation cross-section for Ursa Major II and Willman I are log (({sigma}v){sub {chi}}, cm{sup 3} s{sup -1}) {approx}< -25 for the preferred set of charged particle propagation parameters adopted by CPU07; this is comparable to that inferred at {gamma}-ray energies from the two-year Fermi Large Area Telescope data. We discuss three avenues for improving the constraints on ({sigma}v){sub {chi}} presented here, and conclude that deep radio observations of dSphs are highly complementary to indirect WIMP searches at higher energies.},
doi = {10.1088/0004-637X/773/1/61},
url = {https://www.osti.gov/biblio/22131061}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 773,
place = {United States},
year = {2013},
month = {8}
}