228 research outputs found
Local Group dSph radio survey with ATCA (III): Constraints on Particle Dark Matter
We performed a deep search for radio synchrotron emissions induced by weakly
interacting massive particles (WIMPs) annihilation or decay in six dwarf
spheroidal (dSph) galaxies of the Local Group. Observations were conducted with
the Australia Telescope Compact Array (ATCA) at 16 cm wavelength, with an rms
sensitivity better than 0.05 mJy/beam in each field. In this work, we first
discuss the uncertainties associated with the modeling of the expected signal,
such as the shape of the dark matter (DM) profile and the dSph magnetic
properties. We then investigate the possibility that point-sources detected in
the proximity of the dSph optical center might be due to the emission from a DM
cuspy profile. No evidence for an extended emission over a size of few arcmin
(which is the DM halo size) has been detected. We present the associated bounds
on the WIMP parameter space for different annihilation/decay final states and
for different astrophysical assumptions. If the confinement of electrons and
positrons in the dSph is such that the majority of their power is radiated
within the dSph region, we obtain constraints on the WIMP annihilation rate
which are well below the thermal value for masses up to few TeV. On the other
hand, for conservative assumptions on the dSph magnetic properties, the bounds
can be dramatically relaxed. We show however that, within the next 10 years and
regardless of the astrophysical assumptions, it will be possible to
progressively close in on the full parameter space of WIMPs by searching for
radio signals in dSphs with SKA and its precursors.Comment: 17 pages, 6 figure panels. Companion papers: arXiv:1407.5479 and
arXiv:1407.5482. v3: minor revision, matches published versio
Gamma Ray Signals from Dark Matter: Concepts, Status and Prospects
Weakly interacting massive particles (WIMPs) remain a prime candidate for the
cosmological dark matter (DM), even in the absence of current collider signals
that would unambiguously point to new physics below the TeV scale. The
self-annihilation of these particles in astronomical targets may leave
observable imprints in cosmic rays of various kinds. In this review, we focus
on gamma rays which we argue to play a pronounced role among the various
possible messengers. We discuss the most promising spectral and spatial
signatures to look for, give an update on the current state of gamma-ray
searches for DM and an outlook concerning future prospects. We also assess in
some detail the implications of a potential signal identification for particle
DM models as well as for our understanding of structure formation. Special
emphasis is put on the possible evidence for a 130 GeV line-like signal that
was recently identified in the data of the Fermi gamma-ray space telescope.Comment: 42 pages, 6 figures, 2 tables; updated reference list and extended
discussio
Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA
The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs)
will play an important role in indirect dark matter searches. In this article,
we consider two particularly promising candidate sources for dark matter
annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study
the prospects of detecting such a signal for the soon-operating MAGIC II
telescope system as well as for the planned installation of CTA, taking special
care of describing the experimental features that affect the detectional
prospects. For the first time in such a study, we fully take into account the
effect of internal bremsstrahlung, which has recently been shown to
considerably enhance, in some cases, the gamma-ray flux at the high energies
where Atmospheric Cherenkov Telescopes operate, thus leading to significantly
harder annihilation spectra than traditionally considered. While the detection
of the spectral features introduced by internal bremsstrahlung would constitute
a smoking gun signature for dark matter annihilation, we find that for most
models the overall flux still remains at a level that will be challenging to
detect unless one adopts rather (though by no means overly) optimistic
astrophysical assumptions about the distribution of dark matter in the dwarfs.Comment: 10 pages, 4 figures, minor changes, matches the published version
(JCAP
Extragalactic Background Light Inferred from AEGIS Galaxy SED-type Fractions
The extragalactic background light (EBL) is of fundamental importance both
for understanding the entire process of galaxy evolution and for gamma-ray
astronomy, but the overall spectrum of the EBL between 0.1-1000 microns has
never been determined directly from galaxy spectral energy distribution (SED)
observations over a wide redshift range. The evolving, overall spectrum of the
EBL is derived here utilizing a novel method based on observations only. This
is achieved from the observed evolution of the rest-frame K-band galaxy
luminosity function up to redshift 4 (Cirasuolo et al. 2010), combined with a
determination of galaxy SED-type fractions. These are based on fitting SWIRE
templates to a multiwavelength sample of about 6000 galaxies in the redshift
range from 0.2 to 1 from the All-wavelength Extended Groth Strip International
Survey (AEGIS). The changing fractions of quiescent galaxies, star-forming
galaxies, starburst galaxies and AGN galaxies in that redshift range are
estimated, and two alternative extrapolations of SED-types to higher redshifts
are considered. This allows calculation of the evolution of the luminosity
densities from the UV to the IR, the evolving star formation rate density of
the universe, the evolving contribution to the bolometric EBL from the
different galaxy populations including AGN galaxies and the buildup of the EBL.
Our EBL calculations are compared with those from a semi-analytic model, from
another observationally-based model and observational data. The EBL
uncertainties in our modeling based directly on the data are quantified, and
their consequences for attenuation of very high energy gamma-rays due to pair
production on the EBL are discussed. It is concluded that the EBL is well
constrained from the UV to the mid-IR, but independent efforts from infrared
and gamma-ray astronomy are needed in order to reduce the uncertainties in the
far-IR.Comment: 25 pages, 18 figures, 4 tables; accepted for publication in MNRAS on
September 3, 2010. Online material available at http://side.iaa.es/EB
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