387.
Fermi LAT results on the intensity and origin of the diffuse extragalactic gamma-ray background
Markus Ackermann
(DESY)
03/08/2011, 14:00
Gamma rays
Oral
The 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...
Mr
Stephen Fegan
(LLR / Ecole Polytechnique)
03/08/2011, 14:20
Gamma rays
Oral
I 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...
Dr
Alessandro Cuoco
(Oskar Klein Center- Stockholm)
03/08/2011, 14:40
Gamma rays
Oral
The 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...
Dr
Joachim Ripken
(Stockholm university)
03/08/2011, 15:00
Gamma rays
Oral
The 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...
Mr
Massimo Cavadini
(Insubria University)
03/08/2011, 15:15
Gamma rays
Oral
We 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...
Dr
Luis Reyes
(KICP - University of Chicago)
03/08/2011, 16:00
Gamma rays
Oral
VERITAS (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,...
Rene Ong
(LLR-Ecole Polytechnique/UCLA)
03/08/2011, 16:20
Gamma rays
Oral
VERITAS (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...
Dr
Sergey Ostapchenko
(Norwegian University for Science and Technology (NTNU))
03/08/2011, 16:40
Gamma rays
Oral
We 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...
Dr
Malcolm Fairbairn
03/08/2011, 17:00
Gamma rays
Oral
We 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.
Dr
Jesus Zavala Franco
(Department of Physics and Astronomy, University of Waterloo (CITA National Fellow))
03/08/2011, 17:20
Gamma rays
Oral
The 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...
Mr
Mattia Fornasa
(Instituto de Astrofisica de Andalucia (IAA - CSIC))
03/08/2011, 17:40
Gamma rays
Oral
Using 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...
Dr
Tracy Slatyer
(Institute for Advanced Study)
04/08/2011, 10:20
Gamma rays
Oral
Observations 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...
Dr
Roland Crocker
(MPIK Heidelberg)
04/08/2011, 10:40
Gamma rays
Oral
I 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...
Dr
Philipp Mertsch
(Rudolf Peierls Centre for Theoretical Physics, University of Oxford)
04/08/2011, 11:00
Gamma rays
Oral
Gamma-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...
Dr
Ilias Cholis
(SISSA/ISAS)
04/08/2011, 11:20
Gamma rays
Oral
The 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...
Mr
Tim Linden
(Fermilab / UCSC)
04/08/2011, 11:40
Gamma rays
Oral
Regions of enhanced synchrotron emission with unusually hard spectra – known as
the non-thermal radio filaments – 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...
Dr
Gudlaugur Johannesson
(Science Institute, University of Iceland)
04/08/2011, 13:30
Gamma rays
Oral
The 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...
Dr
Timur Delahaye
(Madrid UAM/CSIC)
04/08/2011, 13:55
Gamma rays
Oral
The 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...
Eric Baxter
(Department of Astronomy and Astrophysics, The University of Chicago)
04/08/2011, 14:15
Gamma rays
Oral
We 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...
Mr
Emrah Birsin
(Humboldt-University Berlin)
04/08/2011, 14:35
Gamma rays
Oral
The 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...
Ignacio Taboada
(Georgia Institute of Technology)
04/08/2011, 15:30
Gamma rays
Oral
The 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)...
Mr
Tri L. Astraatmadja
(Nikhef)
04/08/2011, 15:50
Gamma rays
Oral
This 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...
Dr
Sergey Suchkov
(P.N.Lebedev Physical Institute of the Russian Academy of Sciences)
04/08/2011, 16:10
Gamma rays
Oral
GAMMA-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...
Ms
Maja Llena Garde
(Oskar Klein Centre, Stockholm University)
05/08/2011, 14:00
Gamma rays
Oral
Dwarf 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...
Mr
Stephan Zimmer
(CoPS, Fermi-LAT)
05/08/2011, 14:20
Gamma rays
Oral
Clusters 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...
Mr
German Gomez-Vargas
(IFT UAM/CSIC Madrid - INFN Roma Tor Vergata)
05/08/2011, 14:40
Gamma rays
Oral
The 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...
Dr
Christoph Weniger
(Max-Planck-Institut für Physik, München)
05/08/2011, 14:55
Gamma rays
Oral
Indirect 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...
Mr
Aaron Vincent
(McGill University)
05/08/2011, 15:10
Gamma rays
Oral
We 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...
Prof.
Stefan Funk
(SLAC National Accelerator Center and Stanford University)
05/08/2011, 16:00
Gamma rays
Oral
Recent 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...
Dr
Vincent Marandon
(MPIK Heidelberg)
05/08/2011, 16:25
Gamma rays
Oral
In 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...
Dr
Ira Jung
(ECAP, University Erlangen, Germany)
05/08/2011, 16:50
Gamma rays
Oral
The 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...
Dr
Regis Terrier
(APC CNRS-Université Paris 7)
05/08/2011, 17:10
Gamma rays
Oral
The 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...
