2,225 research outputs found
A review of indirect searches for particle dark matter
The indirect detection of dark matter annihilation and decay using
observations of photons, charged cosmic rays, and neutrinos offers a promising
means of identifying the particle nature of this elusive component of the
universe. The last decade has seen substantial advances in observational data
sets, complemented by new insights from numerical simulations, which together
have enabled for the first time strong constraints on dark matter particle
models, and have revealed several intriguing hints of possible signals. This
review provides an introduction to indirect detection methods and an overview
of recent results in the field.Comment: 32 pages, 6 figures; invited review, accepted to Contemporary Physic
Separating astrophysical sources from indirect dark matter signals
Indirect searches for products of dark matter annihilation and decay face the
challenge of identifying an uncertain and subdominant signal in the presence of
uncertain backgrounds. Two valuable approaches to this problem are (1) using
analysis methods which take advantage of different features in the energy
spectrum and angular distribution of the signal and backgrounds, and (2) more
accurate characterization of backgrounds, which allows for more robust
identification of possible signals. These two approaches are complementary and
can be significantly strengthened when used together. I review the status of
indirect searches with gamma rays using two promising targets, the Inner Galaxy
and the Isotropic Gamma-Ray Background. For both targets, uncertainties in the
properties of backgrounds is a major limitation to the sensitivity of indirect
searches. I then highlight approaches which can enhance the sensitivity of
indirect searches using these targets.Comment: 7 pages, 4 figures. Contributed to the National Academy of Sciences'
Dark Matter Sackler Colloquiu
Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background
We place new constraints on the contribution of blazars to the large-scale
isotropic gamma-ray background (IGRB) by jointly analyzing the measured source
count distribution (logN-logS) of blazars and the measured intensity and
anisotropy of the IGRB. We find that these measurements point to a consistent
scenario in which unresolved blazars make less than 20% of the IGRB intensity
at 1-10 GeV while accounting for the majority of the measured anisotropy in
that energy band. These results indicate that the remaining fraction of the
IGRB intensity is made by a component with a low level of intrinsic anisotropy.
We determine upper limits on the anisotropy from non-blazar sources, adopting
the best-fit parameters of the measured source count distribution to calculate
the unresolved blazar anisotropy. In addition, we show that the anisotropy
measurement excludes some recently proposed models of the unresolved blazar
population.Comment: 7 pages, 4 figures. v2: new section (Sec.III) and 2 figures added.
Expanded discussions in the other sections. Results and conclusions
unchanged. New Section III is also a reply to the comment of Harding &
Abazajian arXiv:1204.3870 on this wor
Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT
The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. We analyze the angular power spectrum of the diffuse emission measured by the Fermi Large Area Telescope at Galactic latitudes |b|>30° in four energy bins spanning 1â50 GeV. At multipoles ââ„155, corresponding to angular scales âČ2°, angular power above the photon noise level is detected at >99.99%â confidence level in the 1â2 GeV, 2â5 GeV, and 5â10 GeV energy bins, and at >99% confidence level at 10â50 GeV. Within each energy bin the measured angular power takes approximately the same value at all multipoles ââ„155, suggesting that it originates from the contribution of one or more unclustered source populations. The amplitude of the angular power normalized to the mean intensity in each energy bin is consistent with a constant value at all energies, C_P/âšIâ©^2=9.05±0.84Ă10^(-6)ââsr, while the energy dependence of C_P is consistent with the anisotropy arising from one or more source populations with power-law photon spectra with spectral index Î_s=2.40±0.07. We discuss the implications of the measured angular power for gamma-ray source populations that may provide a contribution to the diffuse gamma-ray background
Dark matter subhalos and unidentified sources in the Fermi 3FGL source catalog
If dark matter consists of weakly interacting massive particles (WIMPs), dark
matter subhalos in the Milky Way could be detectable as gamma-ray point sources
due to WIMP annihilation. In this work, we perform an updated study of the
detectability of dark matter subhalos as gamma-ray sources with the Fermi Large
Area Telescope (Fermi LAT). We use the results of the Via Lactea II simulation,
scaled to the Planck 2015 cosmological parameters, to predict the local dark
matter subhalo distribution. Under optimistic assumptions for the WIMP
parameters --- a 40 GeV particle annihilating to with a thermal
cross-section, as required to explain the Galactic center GeV excess --- we
predict that at most subhalos might be present in the third Fermi LAT
source catalog (3FGL). This is a smaller number than has been predicted by
prior studies, and we discuss the origin of this difference. We also compare
our predictions for the detectability of subhalos with the number of subhalo
candidate sources in 3FGL, and derive upper limits on the WIMP annihilation
cross-section as a function of the particle mass. If a dark matter
interpretation could be excluded for all 3FGL sources, our constraints would be
competitive with those found by indirect searches using other targets, such as
known Milky Way satellite galaxies.Comment: 17 pages, 8 figure
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