Constraining the Dark Matter decay lifetime with very deep observations of the Perseus cluster with the MAGIC telescopes

We present preliminary results on Dark Matter searches from observations of the Perseus galaxy cluster with the MAGIC Telescopes. MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. Galaxy clusters are the largest known gravitationally bound structures in the Universe, with masses of ~10^15 Solar masses. There is strong evidence that galaxy clusters are Dark Matter dominated objects, and therefore promising targets for Dark Matter searches, particularly for decay signals. MAGIC has taken almost 300 hours of data on the Perseus Cluster between 2009 and 2015, the deepest observational campaign on any galaxy cluster performed so far in the very high energy range of the electromagnetic spectrum. We analyze here a small sample of this data and search for signs of dark matter in the mass range between 100 GeV and 20 TeV. We apply a likelihood analysis optimized for the spectral and morphological features expected in the dark matter decay signals. This is the first time that a dedicated Dark Matter optimization is applied in a MAGIC analysis, taking into account the inferred Dark Matter distribution of the source. The results with the full dataset analysis will be published soon by the MAGIC Collaboration

Diffuse Radio Emission from Galaxy Clusters

In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible `intermediate' sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster's periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line http://galaxyclusters.com. We end this review with a discussion on the detection of diffuse radio emission from the cosmic web.Comment: To appear in Space Science Reviews, 56 pages, 31 figures; For associated data see http://galaxyclusters.co

The origin of the diffuse non-thermal X-ray and radio emission in the Ophiuchus cluster of galaxies

We present high resolution 240 and 607 MHz GMRT radio observations, complemented with 74 MHz archival VLA radio observations of the Ophiuchus cluster of galaxies, whose radio mini-halo has been recently detected at 1400 MHz. We also present archival Chandra and XMM-Newton data of the Ophiuchus cluster. Our observations do not show significant radio emission from the mini-halo, hence we present upper limits to the integrated, diffuse non-thermal radio emission of the core of the Ophiuchus cluster. The XMM-Newton observations can be well explained by a two-temperature thermal model with temperatures of ~=1.8 keV and ~=9.0 keV, respectively, which confirms previous results that suggest that the innermost central region of the Ophiuchus cluster is a cooling core. We also used the XMM-Newton data to set up an upper limit to the (non-thermal) X-ray emission from the cluster. The combination of available radio and X-ray data has strong implications for the currently proposed models of the spectral energy distribution (SED) from the Ophiuchus cluster. In particular, a synchrotron+IC model is in agreement with the currently available data, if the average magnetic field is in the range (0.02-0.3) microG. A pure WIMP annihilation scenario can in principle reproduce both radio and X-ray emission, but at the expense of postulating very large boost factors from dark matter substructures, jointly with extremely low values of the average magnetic field. Finally, a scenario where synchrotron and inverse Compton emission arise from PeV electron-positron pairs (via interactions with the CMB), can be ruled out, as it predicts a non-thermal soft X-ray emission that largely exceeds the thermal Bremsstrahlung measured by INTEGRAL.Comment: Accepted for publication in MNRAS; 13 pages, 8 figures. Includes minor changes. Abridged abstrac

The search for DM in nearby dSph galaxies with MAGIC: candidates, results and prospects

At present, dwarf spheroidal galaxies satellites of the Milky Way may represent the best astrophysical objects for dark matter (DM) searches with gamma-ray telescopes. They present the highest mass-to-light ratios known in the Universe. Furthermore, many of them are near enough from the Earth to be able to yield high predicted DM annihilation fluxes that might be observed by current gamma-ray instruments like MAGIC. The picture has become even better with the recent discovery of new dwarfs. These new objects are expected to yield even higher DM annihilation fluxes, since most of them are nearer than the previously known dwarfs and are even more DM dominated systems. Here a tentative list of the best candidates is given. The observational results obtained with MAGIC from the Draco dwarf as well as the observation of other dwarfs carried out by other Cherenkov telescopes are presented as well. Finally, we discuss the detection prospects of such kind of objects in the context of DM searches.Comment: To appear in the proceedings of the 8th UCLA Dark Matter Symposium, Marina del Rey, USA, 20-22 February 200

IAA : Información y actualidad astronómica (34)

Sumario : Ondas gravitatorias: la otra luz del cosmos.-- El camino hacia el interior de las estrellas.-- DECONSTRUCCIÓN Y otros ENSAYOS. Clima marciano.-- EL “MOBY DICK” DE... Javier Gorosabel (IAA-CSIC).-- CIENCIA EN HISTORIAS. Antonia Maury: un espíritu libre.-- ACTUALIDAD.-- ENTRE BASTIDORES.-- CIENCIA: PILARES E INCERTIDUMBRES. Atmósfera de Marte.-- RECOMENDADOS.N