72 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
Signatures of LCDM substructure in tidal debris
In the past decade, surveys of the stellar component of the Galaxy have
revealed a number of streams from tidally disrupted dwarf galaxies and globular
clusters. Simulations of hierarchical structure formation in LCDM cosmologies
predict that the dark matter halo of a galaxy like the Milky Way contains
hundreds of subhalos with masses of ~10^8 solar masses and greater, and it has
been suggested that the existence of coherent tidal streams is incompatible
with the expected abundance of substructure. We investigate the effects of dark
matter substructure on tidal streams by simulating the disruption of a
self-gravitating satellite on a wide range of orbits in different host models
both with and without substructure. We find that the halo shape and the
specific orbital path more strongly determine the overall degree of disruption
of the satellite than does the presence or absence of substructure, i.e., the
changes in the large-scale properties of the tidal debris due to substructure
are small compared to variations in the debris from different orbits in a
smooth potential. Substructure typically leads to an increase in the degree of
clumpiness of the tidal debris in sky projection, and in some cases a more
compact distribution in line-of-sight velocity. Substructure also leads to
differences in the location of sections of debris compared to the results of
the smooth halo model, which may have important implications for the
interpretation of observed tidal streams. A unique signature of the presence of
substructure in the halo which may be detectable by upcoming surveys is
identified. We conclude, however, that predicted levels of substructure are
consistent with a detection of a coherent tidal stream from a dwarf galaxy.Comment: 15 pages, 13 figures, accepted for publication in ApJ. Matches
accepted versio
Dark matter implications of the WMAP-Planck Haze
Gamma rays and microwave observations of the Galactic Center and surrounding
areas indicate the presence of anomalous emission, whose origin remains
ambiguous. The possibility of dark matter (DM) annihilation explaining both
signals through prompt emission at gamma-rays and secondary emission at
microwave frequencies from interactions of high-energy electrons produced in
annihilation with the Galactic magnetic fields has attracted much interest in
recent years. We investigate the DM interpretation of the Galactic Center
gamma-ray excess by searching for the associated synchrotron in the WMAP-Planck
data. Considering various magnetic field and cosmic-ray propagation models, we
predict the synchrotron emission due to DM annihilation in our Galaxy, and
compare it with the WMAP-Planck data at 23-70GHz. In addition to standard
microwave foregrounds, we separately model the microwave counterpart to the
Fermi Bubbles and the signal due to DM, and use component separation techniques
to extract the signal associated with each template from the total emission. We
confirm the presence of the Haze at the level of 7% of the total sky intensity
at 23GHz in our chosen region of interest, with a harder spectrum than the synchrotron from regular cosmic-ray electrons. The data do
not show a strong preference towards fitting the Haze by either the Bubbles or
DM emission only. Inclusion of both components provides a better fit with a DM
contribution to the Haze emission of 20% at 23GHz, however, due to significant
uncertainties in foreground modeling, we do not consider this a clear detection
of a DM signal. We set robust upper limits on the annihilation cross section by
ignoring foregrounds, and also report best-fit DM annihilation parameters
obtained from a complete template analysis. We conclude that the WMAP-Planck
data are consistent with a DM interpretation of the gamma-ray excess.Comment: 34 pages, 9 figure
Robust identification of isotropic diffuse gamma rays from Galactic dark matter
Dark matter annihilation in Galactic substructure will produce diffuse
gamma-ray emission of remarkably constant intensity across the sky, making it
difficult to disentangle this Galactic dark matter signal from the
extragalactic gamma-ray background. We show that if Galactic dark matter
contributes a modest fraction of the measured emission in an energy range
accessible to the Fermi Gamma-ray Space Telescope, the energy dependence of the
angular power spectrum of the total measured emission could be used to
confidently identify gamma rays from Galactic dark matter substructure.Comment: 4 pages, 2 figures, added 1 reference, published in PR
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
Improved Limits on Sterile Neutrino Dark Matter using Full-Sky Fermi Gamma-Ray Burst Monitor Data
A sterile neutrino of ~keV mass is a well motivated dark matter candidate.
Its decay generates an X-ray line that offers a unique target for X-ray
telescopes. For the first time, we use the Gamma-ray Burst Monitor (GBM)
onboard the Fermi Gamma-Ray Space Telescope to search for sterile neutrino
decay lines; our analysis covers the energy range 10-25 keV (sterile neutrino
mass 20-50 keV), which is inaccessible to X-ray and gamma-ray satellites such
as Chandra, Suzaku, XMM-Newton, and INTEGRAL. The extremely wide field of view
of the GBM enables a large fraction of the Milky Way dark matter halo to be
probed. After implementing careful data cuts, we obtain ~53 days of full sky
observational data. We observe an excess of photons towards the Galactic
Center, as expected from astrophysical emission. We search for sterile neutrino
decay lines in the energy spectrum, and find no significant signal. From this,
we obtain upper limits on the sterile neutrino mixing angle as a function of
mass. In the sterile neutrino mass range 25-40 keV, we improve upon previous
upper limits by approximately an order of magnitude. Better understanding of
detector and astrophysical backgrounds, as well as detector response, will
further improve the sensitivity of a search with the GBM.Comment: 16 pages, 11 figures, references added, discussion expanded, some
typos fixed, matches the published versio
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