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387. Fermi LAT results on the intensity and origin of the diffuse extragalactic gamma-ray backgroundMarkus Ackermann (DESY)03/08/2011, 14:00Gamma raysOralThe data collected by the Fermi Large Area Telescope (LAT) over the last 3 years enable a huge step forward in measuring and understanding the origins of the extragalactic diffuse gamma-ray background (EGB). The EGB originates from the superposition of different populations of unresolved sources with possible contributions from genuinely diffuse and exotic processes. In most parts of...Go to contribution page
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Mr Stephen Fegan (LLR / Ecole Polytechnique)03/08/2011, 14:20Gamma raysOralI review the characteristics of GeV-TeV emitting AGN after two years of observations with Fermi. Our view of these objects has advanced significantly since the launch of Fermi and the advent of the sensitive ground-based gamma-ray instruments, such as HESS, VERITAS and MAGIC. With these instruments we detect a large population of GeV-TeV AGN with different sub-classes and can, for the...Go to contribution page
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Dr Alessandro Cuoco (Oskar Klein Center- Stockholm)03/08/2011, 14:40Gamma raysOralThe diffuse gamma-ray background is expected to exhibit small scale anisotropies which can carry information on the underlying sources contributing to it. Astrophysical sources as well as more exotic processes like galactic or extragalactic DM annihilation are expected to leave their imprint in the pattern of the gamma-ray anisotropies. I will present the results of an angular power...Go to contribution page
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Dr Joachim Ripken (Stockholm university)03/08/2011, 15:00Gamma raysOralThe indirect search for dark matter is one out of many scientific goals of gamma-astronomy. The main focus are spectral signatures of dark matter annihilation or decay in the measurements towards targets where dark matter is expected. Another possibility is to examine the anisotropy power spectrum of the $\gamma$-ray background radiation, which might exhibit a measuable signature...Go to contribution page
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Mr Massimo Cavadini (Insubria University)03/08/2011, 15:15Gamma raysOralWe present a two-parameter model of the extragalactic $\gamma$-ray background (EGB) in the 0.1-100 GeV range as measured by the Large Area Telescope (LAT) onboard the {\it Fermi} satellite. The EGB can be fully explained as the sum of three distinct components, namely blazars, non-beamed AGNs (Seyfert galaxies and QSOs), and cosmic rays from star-forming galaxies. The contribution to...Go to contribution page
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Dr Luis Reyes (KICP - University of Chicago)03/08/2011, 16:00Gamma raysOralVERITAS (Very Energetic Radiation Imaging Telescope Array System) is an array of atmospheric Cherenkov telescopes sensitive to very high energy (VHE) gamma rays above 100 GeV. Located in southern Arizona, USA, the full VERITAS array of four 12m- diameter telescopes is completing its fourth year of operation. The VERITAS observation program covers a range of extragalactic objects,...Go to contribution page
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Rene Ong (LLR-Ecole Polytechnique/UCLA)03/08/2011, 16:20Gamma raysOralVERITAS (Very Energetic Radiation Imaging Telescope Array System) is an array of atmospheric Cherenkov telescopes sensitive to very high energy (VHE) gamma rays above 100 GeV. Located in southern Arizona, USA, the full VERITAS array of four 12m-diameter telescopes is completing its fourth year of observations and is operating with outstanding source sensitivity. VERITAS has detected...Go to contribution page
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Dr Sergey Ostapchenko (Norwegian University for Science and Technology (NTNU))03/08/2011, 16:40Gamma raysOralWe investigate electromagnetic cascades originating from interactions with the extragalactic photon background of high energy photons emitted by blazars. We demonstrate that the non-observation of 1ES 0229+200 by Fermi-LAT indicates that a relatively strong intergalactic magnetic field (IGMF) fills more than 60% of space, favoring the primordial IGMF origin. We present also a new public...Go to contribution page
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Dr Malcolm Fairbairn03/08/2011, 17:00Gamma raysOralWe show how the propagation of TeV photons differs in Universes with different expansion histories. We discuss whether it is possible to identify different cosmologies based on their opacity, discuss uncertainties associated with the observed star formation rates and show how constraints from this method adds to existing data.Go to contribution page
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Dr Jesus Zavala Franco (Department of Physics and Astronomy, University of Waterloo (CITA National Fellow))03/08/2011, 17:20Gamma raysOralThe extragalactic background light (EBL) observed at multiple wavelengths is a promising tool to probe the nature of dark matter since it might contain a significant contribution from gamma-rays produced promptly by dark matter annihilation. Additionally, the electrons and positrons produced in the annihilation give energy to the CMB photons to populate the EBL with X-rays and...Go to contribution page
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Mr Mattia Fornasa (Instituto de Astrofisica de Andalucia (IAA - CSIC))03/08/2011, 17:40Gamma raysOralUsing the first 22 months of data, the Fermi-LAT collaboration measured the angular spectrum (APS) of anisotropies in the diffuse gamma-ray background. Results indicate the detection of angular signal with a significance of few sigma. The APS is consistent with being independent from multipole (for multipoles larger than 154) and this is compatible with the contribution from one or more...Go to contribution page
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Dr Tracy Slatyer (Institute for Advanced Study)04/08/2011, 10:20Gamma raysOralObservations of the gamma-ray sky by the Fermi Gamma-ray Space Telescope have revealed a striking sharp-edged, double-lobed structure in 1-100 GeV gamma rays, centered on the Galactic Center and extending 50 degrees north and south of the Galactic plane. The gamma-rays associated with these "Fermi bubbles" have a significantly harder spectrum than emission spatially correlated with maps...Go to contribution page
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Dr Roland Crocker (MPIK Heidelberg)04/08/2011, 10:40Gamma raysOralI will show that the recently-discovered Fermi Bubbles are naturally explained as due to a population of relic cosmic ray protons and heavier ions injected by processes associated with sustained, extremely long timescale and high areal density star- formation in the Galactic center. In our picture, the Bubbles are essentially calorimetric recordings of Galactic centre activity over the...Go to contribution page
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Dr Philipp Mertsch (Rudolf Peierls Centre for Theoretical Physics, University of Oxford)04/08/2011, 11:00Gamma raysOralGamma-ray data from Fermi-LAT reveal a bi-lobular structure extending up to 50 degrees above and below the galactic centre, which presumably originated in some form of energy release there less than a few million years ago. It has been argued that the gamma-rays arise from hadronic interactions of high energy cosmic rays which are advected out by a strong wind, or from inverse-Compton...Go to contribution page
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Dr Ilias Cholis (SISSA/ISAS)04/08/2011, 11:20Gamma raysOralThe Fermi haze is a diffuse component of gamma-ray emission centered towards the galactic center, extending up to approximately $\pm$50 degrees in latitude, recently revealed after analysis of full-sky map data from the Fermi LAT instrument. The Fermi ``haze'' is the gamma-ray counterpart generated by inverse Compton emission from the same population of electrons which generate the...Go to contribution page
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Mr Tim Linden (Fermilab / UCSC)04/08/2011, 11:40Gamma raysOralRegions of enhanced synchrotron emission with unusually hard spectra โ known as the non-thermal radio filaments โ have attracted significant interest due difficulty in modeling their synchrotron spectra with astrophysical electron injection spectra. We show that the synchrotron emission from these regions may be connected to recent Fermi-LAT observations showing excess gamma-ray...Go to contribution page
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Dr Gudlaugur Johannesson (Science Institute, University of Iceland)04/08/2011, 13:30Gamma raysOralThe high energy diffuse emission originates when cosmic-rays (CRs) interact with the interstellar medium (ISM) and interstellar radiation field (ISRF). It is the dominant source of gamma-rays in the Fermi-LAT data, accounting for more than half of the photons. Observations of the diffuse emission can be used to explore CR origin and propagation in the Milky Way when combined with modeling...Go to contribution page
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Dr Timur Delahaye (Madrid UAM/CSIC)04/08/2011, 13:55Gamma raysOralThe Galactic gamma-ray diffuse emission is currently observed in the GeV-TeV energy range with unprecedented accuracy by the Fermi satellite. Understanding this component is crucial as it provides a background to many different signals such as extragalactic sources or annihilating dark matter. It is timely to reinvestigate how it is calculated and to assess the various uncertainties...Go to contribution page
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Eric Baxter (Department of Astronomy and Astrophysics, The University of Chicago)04/08/2011, 14:15Gamma raysOralWe present a new technique for using gamma-ray data to constrain the properties of dark matter that makes minimal assumptions about the dark matter and the backgrounds. The technique relies on two properties of the expected signal from annihilations of the smooth dark matter component in our galaxy: 1) it is approximately rotationally symmetric around the axis connecting us to the galactic...Go to contribution page
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Mr Emrah Birsin (Humboldt-University Berlin)04/08/2011, 14:35Gamma raysOralThe H.E.S.S. Cherenkov telescope array, which observes the universe in the very-high-energy (VHE, E > 100 GeV) gamma-ray domain, is involved in indirect searches for particle Dark Matter (DM). Observations towards regions with presumably high DM density like dwarf galaxies or cores of nearby galaxies have been conducted over the last years. Available data of the Galactic Center was...Go to contribution page
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Ignacio Taboada (Georgia Institute of Technology)04/08/2011, 15:30Gamma raysOralThe High Altitude Water Cherenkov (HAWC) observatory is a ground based very high-energy gamma ray detector under construction in Mexico at an altitude of 4100 m. Higher altitude, improved design and a larger physical area used for triggering and background discrimination makes HAWC 15 times more sensitive to Crab-like spectra than its predecessor Milagro. HAWC's large field of view (~2sr)...Go to contribution page
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Mr Tri L. Astraatmadja (Nikhef)04/08/2011, 15:50Gamma raysOralThis is a preliminary study to examine the prospect of detecting TeV photons from $\gamma$-ray bursts (GRB) using km-size neutrino telescope, specifically for the ANTARES neutrino telescope. Although optimized to detect upgoing neutrino-induced muons, km$^3$ neutrino telescopes nevertheless has a potential to detect high-energy photons by detecting downgoing muons from electromagnetic...Go to contribution page
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Dr Sergey Suchkov (P.N.Lebedev Physical Institute of the Russian Academy of Sciences)04/08/2011, 16:10Gamma raysOralGAMMA-400 is a space mission included in the Russian Federal Space Program and supported by the Russian Federal Space Agency. The main characteristics of the mission are a high elliptical orbit (initial parameters: perigee 500 km, apogee 300 000 km), a total mass for the scientific payload of 2600 kg, and a power budget for the instrument of 2 kW. The experiment is intended to...Go to contribution page
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Ms Maja Llena Garde (Oskar Klein Centre, Stockholm University)05/08/2011, 14:00Gamma raysOralDwarf spheroidal galaxies have a large mass to light ratio and low astrophysical background, and are therefore considered one of the most promising targets for dark matter searches in the gamma-ray band. The Fermi-LAT sensitivity to gamma-ray sources can be improved through the use of a combined likelihood analysis, which in the event of a null detection, yields enhanced constraints on...Go to contribution page
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Mr Stephan Zimmer (CoPS, Fermi-LAT)05/08/2011, 14:20Gamma raysOralClusters of Galaxies are the largest virialized structures in the universe. Radio observations indicate the presence of a relativisitic electron population that can give rise to a distinct gamma-ray signature through scattering with low energy photons. In addition, gamma-rays can result from collisions of cosmic ray protons with particles in the intracluster medium through subsequent...Go to contribution page
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Mr German Gomez-Vargas (IFT UAM/CSIC Madrid - INFN Roma Tor Vergata)05/08/2011, 14:40Gamma raysOralThe munuSSM is a supersymmetric model that has been proposed to solve the problems of other supersymmetric extensions of the standard model. The gravitino is a natural candidate for dark matter in the munuSSM and could be detectable through the emission of a monochromatic gamma ray in a two-body decay. We study the prospects of the Fermi-LAT telescope to detect such monochromatic lines in...Go to contribution page
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Dr Christoph Weniger (Max-Planck-Institut fรผr Physik, Mรผnchen)05/08/2011, 14:55Gamma raysOralIndirect searches for dark matter annihilation or decay products in the cosmic-ray spectrum are plagued by the question of how to disentangle a dark matter signal from the omnipresent astrophysical background. One of the practically background-free `smoking gun' signatures for dark matter would be the observation of a sharp cutoff in the gamma-ray energy spectrum. Such a feature is...Go to contribution page
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Mr Aaron Vincent (McGill University)05/08/2011, 15:10Gamma raysOralWe reconsider Sommerfeld-enhanced annihilation of dark matter (DM) into leptons to explain PAMELA and Fermi electron and positron observations, in light of possible new effects from substructure. There is strong tension between getting a large enough lepton signal while respecting constraints on the fluxes of associated gamma rays. We first show that these constraints become significantly...Go to contribution page
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Prof. Stefan Funk (SLAC National Accelerator Center and Stanford University)05/08/2011, 16:00Gamma raysOralRecent years have brought significant advances in our understanding of particle acceleration in Supernova remnants. These have come both through new observational data, most notably through gamma-ray observations with instruments such as Fermi- LAT and the current generation of Imaging Atmospheric Cherenkov Telescopes (IACT) as well as through an improvement in the theoretical...Go to contribution page
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Dr Vincent Marandon (MPIK Heidelberg)05/08/2011, 16:25Gamma raysOralIn the last years, the observation of the Galactic plane by the third generation of Cerenkov Telescopes, mainly done by H.E.S.S., has revealed that pulsar wind nebulae (PWN) are the largest source class in the Galaxy. The TeV observational characteristics of those objects can be divided into two sub-classes : the compact and centre-filled sources, mainly associated with young pulsars, and...Go to contribution page
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Dr Ira Jung (ECAP, University Erlangen, Germany)05/08/2011, 16:50Gamma raysOralThe detection of very-high-energy gamma-rays from supernova remnants (SNR) has proven, that particles are accelerated in shock waves of the SNRs up to energies of about 100 TeV. Theoretical models predict, that SNRs can accelerate particles up to energies of several 10^15 TeV within the first 1000 years after the supernova explosion. Due to this short time span, the number of SNRs at...Go to contribution page
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Dr Regis Terrier (APC CNRS-Universitรฉ Paris 7)05/08/2011, 17:10Gamma raysOralThe HESS Galactic Plane Survey has revealed dozens of large, extended sources. In some regions, especially in the vicinity of Galactic arms tangent points, potential TeV gamma-ray emitters tend to cluster. The TeV gamma-ray source HESS J1843-033 is a large, complex region of emission close to the Scutum arm tangent point. We report detailed analysis of its morphology and identify...Go to contribution page
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