964 research outputs found
Identification of Spinning Dust in Halpha-Correlated Microwave Emission
CMB experiments commonly use maps of Halpha intensity as a spatial template
for Galactic free-free emission, assuming a power law I_nu \propto nu^-0.15 for
the spectrum. Any departure from the assumed free-free spectrum could have a
detrimental effect on determination of the primary CMB anisotropy. We show that
the Halpha-correlated emission spectrum in the diffuse warm ionized medium
(WIM) is not the expected free-free spectrum at WMAP frequencies. Instead,
there is a broad bump in the spectrum at ~50 GHz which is consistent with
emission from spinning dust grains. Spectra from both the full sky and smaller
regions of interest are well fit by a superposition of a free-free and WIM
Draine & Lazarian (1998) spinning dust model, shifted in frequency. The
spinning dust emission is ~5 times weaker than the free-free component at 50
GHz, with the null hypothesis that the Halpha-correlated spectrum is pure
free-free, ruled out at >8 sigma in all regions and >100 sigma for the full sky
fit.Comment: 8 pages, 5 figures; submitted to ApJ; LaTeX modified slightly to
reveal missing Figure
Evidence Of Dark Matter Annihilations In The WMAP Haze
The WMAP experiment has revealed an excess of microwave emission from the
region around the center of our Galaxy. It has been suggested that this signal,
known as the ``WMAP Haze'', could be synchrotron emission from relativistic
electrons and positrons generated in dark matter annihilations. In this letter,
we revisit this possibility. We find that the angular distribution of the WMAP
Haze matches the prediction for dark matter annihilations with a cusped density
profile, in the inner kiloparsecs. Comparing the
intensity in different WMAP frequency bands, we find that a wide range of
possible WIMP annihilation modes are consistent with the spectrum of the haze
for a WIMP with a mass in the 100 GeV to multi-TeV range. Most interestingly,
we find that to generate the observed intensity of the haze, the dark matter
annihilation cross section is required to be approximately equal to the value
needed for a thermal relic, cm/s. No
boost factors are required. If dark matter annihilations are in fact
responsible for the WMAP Haze, and the slope of the halo profile continues into
the inner Galaxy, GLAST is expected to detect gamma rays from the dark matter
annihilations in the Galactic Center if the WIMP mass is less than several
hundred GeV.Comment: 4 pages, 3 figure
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