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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2158
DTSTART:20110428T210000Z
DURATION:PT1H0M0S
DTSTAMP:20260305T230447Z
LAST-MODIFIED:20110413T121936Z
LOCATION:4274 Chamberlin Hall
SUMMARY:A Holistic View of Unstable Dark Matter: Spectral and Anisotro
 py Signatures in Astrophysical Backgrounds\, NPAC (Nuclear/Particle/As
 tro/Cosmo) Forum\, Le Zhang\, UW-Madison/Hamburg University/DESY
DESCRIPTION:The nature of dark matter is one of the key outstanding pr
 oblems in both particle and astrophysics. If dark matter decays or ann
 ihilates into electrons and positrons\, it can affect diffuse radiatio
 n backgrounds observed in astrophysics. We present  a new\, more gener
 al analysis of constraints on dark matter models. For any decaying dar
 k matter model\, constraints on mass and lifetime can be obtained by f
 olding the specific dark matter decay spectrum with a response functio
 n. These response functions are derived from full-sky radio surveys an
 d Fermi-LAT gamma-ray observations and apply them to place constraints
  on some specific dark matter decay models. We also discuss the influe
 nce of astrophysical uncertainties on the response function\, such as 
 the uncertainties from propagation models and from the spatial distrib
 ution of the dark matter. <br><br>
\n<br><br>
\nMoreover\, an anisotro
 py analysis of full-sky emission gamma-ray and radio maps is performed
  to identify possible signatures of annihilating dark matter. We calcu
 late angular power spectra of the cosmological background of synchrotr
 on emission from dark matter annihilations into electron-positron pair
 s. We compare the power spectra with the anisotropy of astrophysical a
 nd cosmological radio backgrounds\, from normal galaxies\, radio-galax
 ies\, galaxy cluster accretion shocks\, the cosmic microwave backgroun
 d and Galactic foregrounds. In addition\, we develop a numerical tool 
 to compute gamma-ray emission from such electrons and positrons diffus
 ing in the smooth host halo and in substructure halos with masses down
  to earth mass. We show that\, unlike the total gamma-ray angular powe
 r spectrum observed by Fermi-LAT\, the angular power spectrum from the
  inverse Compton scattering is exponentially suppressed below an angul
 ar scale determined by the diffusion length of electrons and positrons
 .
URL:https://www.physics.wisc.edu/events/?id=2158
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