10,507 research outputs found
Constraining Galactic dark matter with gamma-ray pixel counts statistics
Gamma-ray searches for new physics such as dark matter are often driven by
investigating the composition of the extragalactic gamma-ray background (EGB).
Classic approaches to EGB decomposition manifest in resolving individual point
sources and dissecting the intensity spectrum of the remaining unresolved
component. Furthermore, statistical methods have recently been proven to
outperform the sensitivity of classic source detection algorithms in finding
point-source populations in the unresolved flux regime. In this article, we
employ the 1-point photon count statistics of eight years of Fermi-LAT data to
resolve the population of extragalactic point sources and to decompose the
diffuse isotropic background contribution for Galactic latitudes |b|>30 deg. We
use three adjacent energy bins between 1 and 10 GeV. For the first time, we
extend the analysis to incorporate a potential contribution from annihilating
dark matter smoothly distributed in the Galaxy. We investigate the sensitivity
reach of 1-point statistics for constraining the thermally-averaged
self-annihilation cross section of dark matter, using different
template models for the Galactic foreground emission. Given the official
Fermi-LAT interstellar emission model, we set upper bounds on the DM
self-annihilation cross section that are comparable with the
constraints obtained by other indirect detection methods, in particular by the
stacking analysis of several dwarf spheroidal galaxies.Comment: 11 pages, 7 figures, 1 table; v2: major changes improving the
selection of the RO
Cosmic-ray antiproton constraints on light dark matter candidates
Some direct detection experiments have recently collected excess events that
could be interpreted as a dark matter (DM) signal, pointing to particles in the
10 GeV mass range. We show that scenarios in which DM can self-annihilate
with significant couplings to quarks are likely excluded by the cosmic-ray (CR)
antiproton data, provided the annihilation is S-wave dominated when DM
decouples in the early universe. These limits apply to most of supersymmetric
candidates, eg in the minimal supersymmetric standard model (MSSM) and in the
next-to-MSSM (NMSSM), and more generally to any thermal DM particle with
hadronizing annihilation final states.Comment: Contribution to the proceedings of TAUP-2011 (Munich, 5-9 IX 2011). 4
page
Indirect search for dark matter with micrOMEGAs2.4
We present a new module of micrOMEGAs devoted to the computation of indirect
signals from dark matter annihilation in any new model with a stable weakly
interacting particle. The code provides the mass spectrum, cross-sections,
relic density and exotic fluxes of gamma rays, positrons and antiprotons. The
propagation of charged particles in the Galactic halo is handled with a new
module that allows to easily modify the propagation parameters.Comment: 24 pages, 6 figures, typos corrected, acknowledgements modifie
Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center
The apparent gamma-ray excess in the Galactic center region and inner Galaxy
has attracted considerable interest, notably because both its spectrum and
radial distribution are consistent with an interpretation in terms of
annihilating dark matter particles with a mass of about 10-40 GeV. We confront
such an interpretation with an updated compilation of various indirect dark
matter detection bounds, which we adapt to the specific form required by the
observed signal. We find that cosmic-ray positron data strongly rule out dark
matter annihilating to light leptons, or 'democratically' to all leptons, as an
explanation of the signal. Cosmic-ray antiprotons, for which we present
independent and significantly improved limits with respect to previous
estimates, are already in considerable tension with DM annihilation to any
combination of quark final states; the first set of AMS-02 data will thus be
able to rule out or confirm the DM hypothesis with high confidence. For
reasonable assumptions about the magnetic field in the Galactic center region,
radio observations independently put very severe constraints on a DM
interpretation of the excess, in particular for all leptonic annihilation
channels.Comment: 23 pages revtex, 19 figures, 1 table. Extended discussion of
antiproton limits and added references. Matches published versio
On the origin of X-ray emission in some FR Is: ADAF or jet?
We investigate the X-ray origin in FR Is using the radio, submillimetre,
optical, and {\em Chandra} X-ray data of a small sample consisting of eight FR
I sources. These sources are very dim, with X-ray luminosities ( is the X-ray luminosity
between 2-10 keV). We try to fit the multiwaveband spectrum using a coupled
accretion-jet model. In this model, the accretion flow is described by an
advection-dominated accretion flow (ADAF) while in the innermost region of ADAF
a fraction of accretion flow is transferred into the vertical direction and
forms a jet. We find that X-ray emission in the source with the highest () is from the ADAF. The results for
the four sources with moderate ( several ) are complicated. Two are mainly from the ADAFs, one from
the jet, and the other from the sum of the jet and ADAF. The X-ray emission in
the three least luminous sources () is dominated by the jet although for one source it can also be
interpreted by the ADAF since the quality of X-ray data is low. We conclude
that these results roughly support the predictions of Yuan & Cui (2005) where
they predict that when the X-ray luminosity of the system is below a critical
value, the X-radiation will not be dominated by the emission from the ADAF any
longer, but by the jet. We also investigate the fuel supply in these sources.
We find that the accretion rates in four sources among the five in which we can
have good constraints to their accretion rates must be higher than the Bondi
rates. This implies that other fuel supply, such as the gas released by the
stellar population inside the Bondi radius, should be important.Comment: 31 pages, 8 figures, accepted for publication in Ap
Religion-based Urbanization Process in Italy: Statistical Evidence from Demographic and Economic Data
This paper analyzes some economic and demographic features of Italians living
in cities containing a Saint name in their appellation (hagiotoponyms).
Demographic data come from the surveys done in the 15th (2011) Italian Census,
while the economic wealth of such cities is explored through their recent
[2007-2011] aggregated tax income (ATI). This cultural problem is treated from
various points of view. First, the exact list of hagiotoponyms is obtained
through linguistic and religiosity criteria. Next, it is examined how such
cities are distributed in the Italian regions. Demographic and economic
perspectives are also offered at the Saint level, i.e. calculating the
cumulated values of the number of inhabitants and the ATI, "per Saint", as well
as the corresponding relative values taking into account the Saint popularity.
On one hand, frequency-size plots and cumulative distribution function plots,
and on the other hand, scatter plots and rank-size plots between the various
quantities are shown and discussed in order to find the importance of
correlations between the variables. It is concluded that rank-rank correlations
point to a strong Saint effect, which explains what actually Saint-based
toponyms imply in terms of comparing economic and demographic data.Comment: 55 pages, 70 refs., 21 figures, 15 tables; prepared for and to be
published in Quantity & Qualit
Do current WIMP direct measurements constrain light relic neutralinos?
New upper bounds on direct detection rates have recently been presented by a
number of experimental collaborations working on searches for WIMPs. In this
paper we analyze how the constraints on relic neutralinos which can be derived
from these results is affected by the uncertainties in the distribution
function of WIMPs in the halo. Various different categories of velocity
distribution functions are considered, and the ensuing implications for
supersymmetric configurations derived. We conservatively conclude that current
experimental data do not constrain neutralinos of small mass (below 50 GeV).Comment: 9 pages, 7 figures, typeset with ReVTeX4. The paper may also be found
at http://www.to.infn.it/~fornengo/papers/constraints05.ps.gz or through
http://www.astroparticle.to.infn.it/index.htm
Highlights and Conclusions of the Chalonge 14th Paris Cosmology Colloquium 2010: `The Standard Model of the Universe: Theory and Observations'
The Chalonge 14th Paris Cosmology Colloquium was held on 22-24 July 2010 in
Paris Observatory on the Standard Model of the Universe: News from WMAP7,
BICEP, QUAD, SPT, AMI, ACT, Planck, QUIJOTE and Herschel; dark matter (DM)
searches and galactic observations; related theory and simulations. %aiming
synthesis, progress and clarification. P Biermann, D Boyanovsky, A Cooray, C
Destri, H de Vega, G Gilmore, S Gottlober, E Komatsu, S McGaugh, A Lasenby, R
Rebolo, P Salucci, N Sanchez and A Tikhonov present here their highlights of
the Colloquium. Inflection points emerged: LambdaWDM (Warm DM) emerges
impressively over LambdaCDM whose galactic scale problems are ever-increasing.
Summary and conclusions by H. J. de Vega, M. C. Falvella and N. G. Sanchez
stress among other points: (i) Primordial CMB gaussianity is confirmed.
Inflation effective theory predicts a tensor to scalar ratio 0.05-0.04 at
reach/border line of next CMB observations, early fast-roll inflation provides
lowest multipoles depression. SZ amplitudes are smaller than expected: CMB and
X-ray data agree but intracluster models need revision and relaxed/non-relaxed
clusters distinction. (ii) cosmic ray positron excess is explained naturally by
astrophysical processes, annihilating/decaying dark matter needs growing
tailoring. (iii) Cored (non cusped) DM halos and warm (keV scale mass) DM are
increasingly favored from theory and observations, naturally producing observed
small scale structures, wimps turn strongly disfavoured. LambdaWDM 1 keV
simulations well reproduce observations. Evidence that LambdaCDM does not work
at small scales is staggering. P Biermann presents his live minutes of the
Colloquium and concludes that a keV sterile neutrino is the most interesting DM
candidate. Photos of the Colloquium are included.Comment: 58 pages, 20 figures. Three contributions added: G. Gilmore, S.
Gottlober and E. Komats
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