Ref HAL: hal-00628253_v1
Ref Arxiv: 1007.5253
DOI: 10.1103/PHYSREVD.82.081302
Ref. & Cit.: NASA ADS
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40 citations
Résumé:

Recent measurements performed with some direct dark matter detection experiments, e.g. CDMS-II and CoGENT (after DAMA/LIBRA), have unveiled a few events compatible with weakly interacting massive particles. The preferred mass range is around 10 GeV, with a quite large spin-independent cross section of 10-43-10-41cm2. In this paper, we recall that a light dark matter particle with dominant couplings to quarks should also generate cosmic-ray antiprotons. Taking advantage of recent works constraining the Galactic dark matter mass profile on the one hand and on cosmic-ray propagation on the other hand, we point out that considering a thermal annihilation cross section for such low mass candidates very likely results in an antiproton flux in tension with the current data, which should be taken into account in subsequent studies.

Ref HAL: in2p3-00391867_v1
DOI: 10.1051/0004-6361/200811476
Exporter : BibTex | endNote
Résumé:

Context. Located in the French Pyrenees, CELESTE was the first ground-based gamma-ray telescope with an energy threshold below 100 GeV. It acquired data from 1999 to 2004, and allowed flux measurements of the Crab nebula and the blazars Mrk 421 and Mrk 501. Aims. We search for Galactic diffuse gamma-ray emission, which is most significant around the Galactic plane, for b = [-5 degrees, + 5 degrees]. Methods. By using the significant data set available for the Crab nebula, we selected Crab OFF-source data at various Galactic latitudes, in order to analyse the diffuse emission. Selection criteria were applied to the sky position, atmospheric conditions, and detector stability. Results. We obtained 108 mn of data in the Galactic anticentre region, providing the first upper limits of around 100 GeV to the diffuse gamma-ray emission with atmospheric Cherenkov detectors. These limits are phi(UL)(int) (E > 140 GeV) = 9.4 x 10(-3) m(-2) s(-1) sr(-1) and phi(UL)(int) (E > 120 GeV) = 1.2 x 10(-2) m(-2) s(-1) sr(-1).

Ref HAL: hal-00628244_v1
Ref Arxiv: 0812.3282
DOI: 10.1103/PHYSREVD.79.083505
Ref. & Cit.: NASA ADS
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10 citations
Résumé:

We derive the covariant formalism associated with the relativistic Sunyaev-Zel'dovich effect due to a nonthermal population of high energy electrons in clusters of galaxies. More precisely, we show that the formalism proposed by Wright in 1979, based on an empirical approach to compute the inverse Compton scattering of a population of relativistic electrons on CMB photons, can actually be reinterpreted as a Boltzmann-like equation, in the single scattering approximation.

Ref HAL: hal-00628226_v1
Ref Arxiv: 0704.2543
DOI: 10.1103/PHYSREVD.76.083506
Ref. & Cit.: NASA ADS
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38 citations
Résumé:

The annihilation of dark matter (DM) in the Galaxy could produce specific imprints on the spectra of antimatter species in Galactic cosmic rays, which could be detected by upcoming experiments such as PAMELA and AMS02. Recent studies show that the presence of substructures can enhance the annihilation signal by a "boost factor" that not only depends on energy, but that is intrinsically a statistical property of the distribution of DM substructures inside the Milky Way. We investigate a scenario in which substructures consist of ˜100 "minispikes" around intermediate-mass black holes. Focusing on primary positrons and antiprotons, we find large boost factors, up to a few thousand, that exhibit a large variance at high energy in the case of positrons and at low energy in the case of antiprotons. As a consequence, an estimate of the DM particle mass based on the observed cutoff in the positron spectrum could lead to a substantial underestimate of its actual value.

Ref HAL: in2p3-00113422_v1
Ref Arxiv: astro-ph/0608247
DOI: 10.1051/0004-6361:20065884
Ref. & Cit.: NASA ADS
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14 citations
Résumé:

We have measured the gamma-ray fluxes of the blazars Mrk 421 and Mrk 501 in the energy range between 50 and 350 GeV (1.2 to 8.3 x 10^25 Hz). The detector, called CELESTE, used first 40, then 53 heliostats of the former solar facility "Themis" in the French Pyrenees to collect Cherenkov light generated in atmospheric particle cascades. The signal from Mrk 421 is often strong. We compare its flux with previously published multi-wavelength studies and infer that we are straddling the high energy peak of the spectral energy distribution. The signal from Mrk 501 in 2000 was weak (3.4 sigma). We obtain an upper limit on the flux from 1ES 1426+428 of less than half that of the Crab flux near 100 GeV. The data analysis and understanding of systematic biases have improved compared to previous work, increasing the detector's sensitivity.

Commentaires: 15 pages, 14 figures, accepted by A&A (July 2006) August 19 -- corrected error in author list

Ref HAL: in2p3-00109798_v1
Ref Arxiv: astro-ph/0601298
DOI: 10.1051/0004-6361:20054340
Ref. & Cit.: NASA ADS
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13 citations
Résumé:

If dark matter is made of neutralinos, annihilation of such Majorana particles should produce high energy cosmic rays, especially in galaxy halo high density regions like galaxy centres. M 31 (Andromeda) is our nearest neighbour spiral galaxy, and both its high mass and its low distance make it a source of interest for the indirect search for dark matter through $\gamma$-ray detection. The ground based atmospheric Cherenkov telescope CELESTE observed M 31 from 2001 to 2003, in the mostly unexplored energy range 50-500 GeV. These observations provide an upper limit on the flux above 50 GeV around $10^{-10}~\rm {cm}^{-2}\,\rm {s}^{-1}$ in the frame of supersymmetric dark matter, and more generally on any gamma emission from M 31.

DOI: 10.1007/10857580_45
Résumé:

Considering a NFW halo of M 31 made of neutralinos, predictions for the \x{03B3} fluxes are computed for different sets of SUSY parameters using the DarkSuspect MC simulation [1] [2]. Then they are compared with the efficiency of CELESTE Cerenkov telescope [3] which has a threshold energy of 30 GeV.

Commentaires: Astronomy, Cosmology and Fundamental Physics: