26 research outputs found
-ray flux from Dark Matter Annihilation in Galactic Caustics
In the frame of indirect dark matter searches we investigate the flux of
high-energy -ray photons produced by annihilation of dark matter in
caustics within our Galaxy under the hypothesis that the bulk of dark matter is
composed of the lightest supersymmetric particles. Unfortunately, the detection
of the caustics annihilation signal with currently available instruments is
rather challenging. Indeed, with realistic assumptions concerning particle
physics and cosmology, the -ray signal from caustics is below the
detection threshold of both erenkov telescopes and
satellite-borne experiments. Nevertheless, we find that this signal is more
prominent than that expected if annihilation only occurs in the smoothed
Galactic halo, with the possible exception of a circle around
the Galactic center if the mass density profile of our Galaxy exhibits a sharp
cusp there. We show that the angular distribution of this -ray flux
changes significantly if DM annihilation preferentially occurs within
virialized sub-halos populating our Galaxy rather than in caustics.Comment: 17 pages, 8 figures. Accepted for publication in JCA
On the detectability of gamma-rays from Dark Matter annihilation in the Local Group with ground-based experiments
Recent studies have suggested the possibility that the lightest
supersymmetric particle is a suitable dark matter candidate. In this
theoretical framework, annihilations in high density environments like the
center of dark matter haloes may produce an intense flux of gamma-rays. In this
paper we discuss the possibility of detecting the signatures of neutralino
annihilation in nearby galaxies with next generation ground-based detectors.Comment: to appear in Proceedings of ICRC 200
Dark Matter Annihilation in Substructures Revised
Upcoming -ray satellites will search for Dark Matter annihilations in
Milky Way substructures (or 'clumps'). The prospects for detecting these
objects strongly depend on the assumptions made on the distribution of Dark
Matter in substructures, and on the distribution of substructures in the Milky
Way halo. By adopting simplified, yet rather extreme, prescriptions for these
quantities, we compute the number of sources that can be detected with upcoming
experiments such as GLAST, and show that, for the most optimistic particle
physics setup ( GeV and annihilation cross section cm s), the result ranges from zero to
hundred sources, all with mass above . However, for a fiducial DM
candidate with mass GeV and cm s,
at most a handful of large mass substructures can be detected at ,
with a 1-year exposure time, by a GLAST-like experiment. Scenarios where
micro-clumps (i.e. clumps with mass as small as ) can be
detected are severely constrained by the diffuse -ray background
detected by EGRET.Comment: Version accepted for publication in MNRAS. Other subhalos mass
function slopes added. All-sky analysis performed. Boost factors added. High
resolution figures for all models in http://www2.iap.fr/users/bertone/Clumps
On the Detectability of Gamma-Rays from Dark Matter Annihilation in the Local Group with Ground-Based Experiments
Recent studies have suggested the possibility that the lightest supersymmetric particle is a suitable dark matter candidate. In this theoretical framework, annihilations in high density environments like the center of dark matter halo es may produce an intense flux of gamma-rays. In this paper we discuss the possibility of detecting the signatures of neutralino annihilation in nearby galaxies with next generation ground-based detectors
X-ray Radiation from the Annihilation of Dark Matter at the Galactic Center
The existing and upcoming multiwavelength data from the Galactic Center
suggest a comparative study in order to propose or rule out possible models
which would explain the observations. In this paper we consider the X-ray
synchrotron and the gamma-ray emission due to Kaluza Klein Dark Matter and
define a set of parameters for the shape of the Dark Matter halo which is
consistent with the observations. We show that for this class of models the
existing Chandra X-ray data is more restrictive than the constraints on very
high energy gamma-rays coming from HESS.Comment: 7 pages 6 figures, updated to match version in prin
Multi-messenger constraints on the annihilating dark matter interpretation of the positron excess
The rise in the energy spectrum of the positron ratio, observed by the PAMELA
satellite above 10 GeV, and other cosmic ray measurements, have been
interpreted as a possible signature of Dark Matter annihilation in the Galaxy.
However, the large number of free parameters, and the large astrophysical
uncertainties, make it difficult to do conclusive statements about the
viability of this scenario. Here, we perform a multi-wavelength,
multi-messenger analysis, that combines in a consistent way the constraints
arising from different astrophysical observations. We show that if standard
assumptions are made for the distribution of Dark Matter (we build models on
the recent Via Lactea II and Aquarius simulations) and the propagation of
cosmic rays, current DM models cannot explain the observed positron flux
without exceeding the observed fluxes of antiprotons or gamma-ray and radio
photons. To visualize the multi-messenger constraints, we introduce "star
plots", a graphical method that allows to show in the same plot theoretical
predictions and observational constraints for different messengers and
wavelengths.Comment: 15 pages, 8 figures, matches published versio
Difficulty of detecting minihalos via -rays from dark matter annihilation
Analytical calculations and recent numerical experiments have shown that a
sizable of the mass in our Galaxy is in a form of clumpy, virialized
substructures that, according to \cite{dms:05}, can be as light as 10^{-6}
\msun. In this work we estimate the gamma-rays flux expected from dark matter
annihilation occurring within these minihalos, under the hypothesis that the
bulk of dark matter is composed by neutralinos. We generate mock sky maps
showing the angular distribution of the expected gamma-ray signal. We compare
them with the sensitivities of satellite-borne experiments such as GLAST and
find that a possible detection of minihalos is indeed very challenging.Comment: 4 pages, four color figures. Version published on PR
The Cosmic Ray Lepton Puzzle
Recent measurements of cosmic ray electrons and positrons by PAMELA, ATIC,
Fermi and HESS have revealed interesting excesses and features in the GeV-TeV
range. Many possible explanations have been suggested, invoking one or more
nearby primary sources such as pulsars and supernova remnants, or dark matter.
Based on the output of the TANGO in PARIS --Testing Astroparticle with the New
GeV/TeV Observations in Positrons And electRons : Identifying the Sources--
workshop held in Paris in May 2009, we review here the latest experimental
results and we discuss some virtues and drawbacks of the many theoretical
interpretations proposed so far.Comment: 6 pages, 3 figures, Extended version of the proceeding of the annual
meeting of the French Astronomical & Astrophysical Society (sf2a
Scoring predictive models using a reduced representation of proteins: model and energy definition
BACKGROUND: Reduced representations of proteins have been playing a keyrole in the study of protein folding. Many such models are available, with different representation detail. Although the usefulness of many such models for structural bioinformatics applications has been demonstrated in recent years, there are few intermediate resolution models endowed with an energy model capable, for instance, of detecting native or native-like structures among decoy sets. The aim of the present work is to provide a discrete empirical potential for a reduced protein model termed here PC2CA, because it employs a PseudoCovalent structure with only 2 Centers of interactions per Amino acid, suitable for protein model quality assessment. RESULTS: All protein structures in the set top500H have been converted in reduced form. The distribution of pseudobonds, pseudoangle, pseudodihedrals and distances between centers of interactions have been converted into potentials of mean force. A suitable reference distribution has been defined for non-bonded interactions which takes into account excluded volume effects and protein finite size. The correlation between adjacent main chain pseudodihedrals has been converted in an additional energetic term which is able to account for cooperative effects in secondary structure elements. Local energy surface exploration is performed in order to increase the robustness of the energy function. CONCLUSION: The model and the energy definition proposed have been tested on all the multiple decoys' sets in the Decoys'R'us database. The energetic model is able to recognize, for almost all sets, native-like structures (RMSD less than 2.0 Å). These results and those obtained in the blind CASP7 quality assessment experiment suggest that the model compares well with scoring potentials with finer granularity and could be useful for fast exploration of conformational space. Parameters are available at the url:
Analytical Approach to Subhaloes Population in Dark Matter Haloes
In the standard model of cosmic structure formation, dark matter haloes form
by gravitational instability. The process is hierarchical: smaller systems
collapse earlier, and later merge to form larger haloes. The galaxy clusters,
hosted by the largest dark matter haloes, are at the top of this hierarchy
representing the largest as well as the last structures formed in the universe,
while the smaller and first haloes are those Earth-sized dark subhaloes which
have been both predicted by theoretical considerations and found in numerical
simulations, though it does not exist any observational hints of their
existence. The probability that a halo of mass at redshift will be part
of a larger halo of mass at the present time can be described in the frame
of the extended Press & Schecter theory making use of the progenitor
(conditional) mass function. Using the progenitor mass function we calculate
analytically, at redshift zero, the distribution of subhaloes in mass,
formation epoch and rarity of the peak of the density field at the formation
epoch. That is done for a Milky Way-size system, assuming both a spherical and
an ellipsoidal collapse model. Our calculation assumes that small progenitors
do not lose mass due to dynamical processes after entering the parent halo, and
that they do not interact with other subhaloes. For a CDM
power spectrum we obtain a subhalo mass function
proportional to with a model-independent .
Assuming the dark matter is a weakly interacting massive particle, the inferred
distributions is used to test the feasibility of an indirect detection in the
-rays energy band of such a population of subhaloes with a GLAST-like
satellite.Comment: 10 pages, 7 figures - submitted to MNRA