970 research outputs found
Multi-wavelength signals of dark matter annihilations at the Galactic center
We perform a systematic study of the multi-wavelength signal induced by
weakly interacting massive particle (WIMP) annihilations at the Galactic Center
(GC). Referring to a generic WIMP dark matter (DM) scenario and depending on
astrophysical inputs, we discuss spectral and angular features and sketch
correlations among signals in the different energy bands. None of the
components which have been associated to the GC source Sgr A*, nor the diffuse
emission components from the GC region, have spectral or angular features
typical of a DM source. Still, data-sets at all energy bands, namely, the
radio, near infrared, X-ray and gamma-ray bands, contribute to place
significant constraints on the WIMP parameter space. In general, the gamma-ray
energy range is not the one with the largest signal to background ratio. In the
case of large magnetic fields close to the GC, X-ray data give the tightest
bounds. The emission in the radio-band, which is less model dependent, is very
constraining as well. The recent detection by HESS of a GC gamma-ray source,
and of a diffuse gamma-ray component, limits the possibility of a DM discovery
with next generation of gamma-ray telescopes, like GLAST and CTA. We find that
the most of the region in the parameter space accessible to these instruments
is actually already excluded at other wave-lenghts. On the other hand, there
may be still an open window to improve constraints with wide-field radio
observations.Comment: 26 pages, 32 figures, treatments of starlight and interstellar medium
improved, other minor changes, references adde
Testing the Dark Matter Interpretation of the PAMELA Excess through Measurements of the Galactic Diffuse Emission
We propose to test the dark matter (DM) interpretation of the positron excess
observed by the PAMELA cosmic-ray (CR) detector through the identification of a
Galactic diffuse gamma-ray component associated to DM-induced prompt and
radiative emission. The goal is to present an analysis based on minimal sets of
assumptions and extrapolations with respect to locally testable or measurable
quantities. We discuss the differences between the spatial and spectral
features for the DM-induced components (with an extended, possibly spherical,
source function) and those for the standard CR contribution (with sources
confined within the stellar disc), and propose to focus on intermediate and
large latitudes. We address the dependence of the signal to background ratio on
the model adopted to describe the propagation of charged CRs in the Galaxy, and
find that, in general, the DM-induced signal can be detected by the Fermi
Gamma-ray Space Telescope at energies above 100 GeV. An observational result in
agreement with the prediction from standard CR components only, would imply
very strong constraints on the DM interpretation of the PAMELA excess. On the
other hand, if an excess in the diffuse emission above 100 GeV is identified,
the angular profile for such emission would allow for a clean disentanglement
between the DM interpretation and astrophysical explanations proposed for the
PAMELA excess. We also compare to the radiative diffuse emission at lower
frequencies, sketching in particular the detection prospects at infrared
frequencies with the Planck satellite.Comment: new benchmark models for dark matter and cosmic-ray introduced, few
comments and references added, conclusion unchange
Particle dark matter searches in the anisotropic sky
Anisotropies in the electromagnetic emission produced by dark matter
annihilation or decay in the extragalactic sky are a recent tool in the quest
for a particle dark matter evidence. We review the formalism to compute the
two-point angular power spectrum in the halo-model approach and discuss the
features and the relative size of the various auto- and cross-correlation
signals that can be envisaged for anisotropy studies. From the side of particle
dark matter signals, we consider the full multi-wavelength spectrum, from the
radio emission to X-ray and gamma-ray productions. We discuss the angular power
spectra of the auto-correlation of each of these signals and of the
cross-correlation between any pair of them. We then extend the search to
comprise specific gravitational tracers of dark matter distribution in the
Universe: weak-lensing cosmic shear, large-scale-structure matter distribution
and CMB-lensing. We have shown that cross-correlating a multi-wavelength dark
matter signal (which is a direct manifestation of its particle physics nature)
with a gravitational tracer (which is a manifestation of the presence of large
amounts of unseen matter in the Universe) may offer a promising tool to
demonstrate that what we call dark matter is indeed formed by elementary
particles.Comment: 16 pages, 11 figures. Prepared as inaugural article for Frontiers in
High-Energy and Astroparticle Physics. v2: few comments added, to appear in
Frontiers (Hypothesis and Theory Article
Aspects of Wimp Dark Matter: Multi-wavelength signals and Extra-dimensions scenarios
Weakly interacting massive particles (WIMPs) are among the leading candidates for the dark matter (DM) component in the Universe. The thesis presents a review of the current status of the DM problem, focussing on the WIMP paradigm and discussing motivations, properties, examples, and detection prospects
A Novel Approach in the WIMP Quest: Cross-Correlation of Gamma-Ray Anisotropies and Cosmic Shear
We present the cross-correlation angular power spectrum of cosmic shear and gamma-rays produced by the annihilation/decay of Weakly Interacting Massive Particle (WIMP) dark matter (DM), and by astrophysical sources. We show that this observable can provide novel information on the composition of the Extra-galactic Gamma-ray Background (EGB), since the amplitude and shape of the cross-correlation signal depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear (since both signals peak at large halo masses) makes such signature potentially detectable by combining Fermi-LAT data with forthcoming galaxy surveys, like Dark Energy Survey and Euclid
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