4 research outputs found
Synchrotron Emission from Dark Matter Annihilation: Predictions for Constraints from Non-detections of Galaxy Clusters with New Radio Surveys
The annihilation of dark matter particles is expected to yield a broad
radiation spectrum via the production of Standard Model particles in
astrophysical environments. In particular, electrons and positrons from dark
matter annihilation produce synchrotron radiation in the presence of magnetic
fields. Galaxy clusters are the most massive collapsed structures in the
universe, and are known to host G-scale magnetic fields. They are
therefore ideal targets to search for, or to constrain the synchrotron signal
from dark matter annihilation. In this work we use the expected sensitivities
of several planned surveys from the next generation of radio telescopes to
predict the constraints on dark matter annihilation models which will be
achieved in the case of non-detections of diffuse radio emission from galaxy
clusters. Specifically, we consider the Tier 1 survey planned for the Low
Frequency Array (LOFAR) at 120 MHz, the EMU survey planned for the Australian
Square Kilometre Array Pathfinder (ASKAP) at 1.4 GHz, and planned surveys for
APERTIF at 1.4 GHz. We find that, for massive clusters and dark matter masses
GeV, the predicted limits on the annihilation cross section
would rule out vanilla thermal relic models for even the shallow LOFAR Tier 1,
ASKAP, and APERTIF surveys.Comment: accepted to ApJ; removal of LOFAR Tier 2 limits; other minor text
changes; conclusions largely unchange
Chandra follow-up of the SDSS DR8 Redmapper catalog using the MATCha pipeline
For abstract see published article
VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations
We report the detection of very high energy gamma-ray emission from the
blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging
Telescope Array System (VERITAS). VERITAS observations of the source were
triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with
the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on
May 16th and May 18th resulted in a strong 13 detection with a
differential photon spectral index, = 3.8 0.4, and a flux level
at 9% of the Crab Nebula above 120 GeV. This also triggered target of
opportunity observations with Swift, optical photometry, polarimetry and radio
measurements, also presented in this work, in addition to the VERITAS and
Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period
finds evidence of a shortest variability timescale of = 6.2
0.9 hours, indicating emission from compact regions within the jet, and the
combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An
investigation into correlations between the multiwavelength observations found
evidence of optical and gamma-ray correlations, suggesting a single-zone model
of emission. Finally, the multiwavelength spectral energy distribution is well
described by a simple one-zone leptonic synchrotron self-Compton radiation
model.Comment: 18 pages, 6 figures. Accepted for publication in the Astrophysical
Journal (ApJ