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Title: CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI

Abstract

Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) Multiplication-Sign 10{sup -8} photons m {sup -2} s {sup -1} (VERITAS, >220 GeV) and {approx}2 Multiplication-Sign 10{sup -6} photons m {sup -2} s {sup -1} (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be <16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocksmore » to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of {approx}(2-5.5) {mu}G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, ({sigma}v).« less

Authors:
 [1]; ;  [2]; ; ; ;  [3];  [4];  [5]; ;  [6]; ;  [7];  [8]; ; ;  [9];  [10];  [11];  [12] more »; « less
  1. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
  2. Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
  3. Department of Physics, Washington University, St. Louis, MO 63130 (United States)
  4. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
  5. Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States)
  6. School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
  7. School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)
  8. Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)
  9. Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)
  10. School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
  11. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
  12. DESY, Platanenallee 6, D-15738 Zeuthen (Germany)
Publication Date:
OSTI Identifier:
22092196
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 757; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; ASTROPHYSICS; CHERENKOV COUNTERS; COSMIC ELECTRONS; COSMIC PHOTONS; COSMIC RADIO SOURCES; CROSS SECTIONS; DIFFUSION; FARADAY EFFECT; GALAXY CLUSTERS; GAMMA ASTRONOMY; GAMMA RADIATION; GEV RANGE; MAGNETIC FIELDS; NONLUMINOUS MATTER; TELESCOPE COUNTERS; VELOCITY

Citation Formats

Arlen, T., Aune, T., Bouvier, A., Beilicke, M., Buckley, J. H., Bugaev, V., Dickherber, R., Benbow, W., Byrum, K., Cannon, A., Collins-Hughes, E., Cesarini, A., Connolly, M. P., Ciupik, L., Cui, W., Feng, Q., Finley, J. P., Dumm, J., Falcone, A., Federici, S., E-mail: pohlmadq@gmail.com, E-mail: christoph.pfrommer@h-its.org, and and others. CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI. United States: N. p., 2012. Web. doi:10.1088/0004-637X/757/2/123.
Arlen, T., Aune, T., Bouvier, A., Beilicke, M., Buckley, J. H., Bugaev, V., Dickherber, R., Benbow, W., Byrum, K., Cannon, A., Collins-Hughes, E., Cesarini, A., Connolly, M. P., Ciupik, L., Cui, W., Feng, Q., Finley, J. P., Dumm, J., Falcone, A., Federici, S., E-mail: pohlmadq@gmail.com, E-mail: christoph.pfrommer@h-its.org, & and others. CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI. United States. doi:10.1088/0004-637X/757/2/123.
Arlen, T., Aune, T., Bouvier, A., Beilicke, M., Buckley, J. H., Bugaev, V., Dickherber, R., Benbow, W., Byrum, K., Cannon, A., Collins-Hughes, E., Cesarini, A., Connolly, M. P., Ciupik, L., Cui, W., Feng, Q., Finley, J. P., Dumm, J., Falcone, A., Federici, S., E-mail: pohlmadq@gmail.com, E-mail: christoph.pfrommer@h-its.org, and and others. Mon . "CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI". United States. doi:10.1088/0004-637X/757/2/123.
@article{osti_22092196,
title = {CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI},
author = {Arlen, T. and Aune, T. and Bouvier, A. and Beilicke, M. and Buckley, J. H. and Bugaev, V. and Dickherber, R. and Benbow, W. and Byrum, K. and Cannon, A. and Collins-Hughes, E. and Cesarini, A. and Connolly, M. P. and Ciupik, L. and Cui, W. and Feng, Q. and Finley, J. P. and Dumm, J. and Falcone, A. and Federici, S., E-mail: pohlmadq@gmail.com, E-mail: christoph.pfrommer@h-its.org and and others},
abstractNote = {Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) Multiplication-Sign 10{sup -8} photons m {sup -2} s {sup -1} (VERITAS, >220 GeV) and {approx}2 Multiplication-Sign 10{sup -6} photons m {sup -2} s {sup -1} (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be <16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of {approx}(2-5.5) {mu}G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, ({sigma}v).},
doi = {10.1088/0004-637X/757/2/123},
journal = {Astrophysical Journal},
number = 2,
volume = 757,
place = {United States},
year = {Mon Oct 01 00:00:00 EDT 2012},
month = {Mon Oct 01 00:00:00 EDT 2012}
}