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Dark matter annihilation and its effect on CMB and Hydrogen 21 cm observations

Mar, 2009
20 pages
Published in:
  • Phys.Rev.D 80 (2009) 043529
e-Print:
DOI:
Report number:
  • BI-TP-2009-08
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Abstract: (arXiv)
If dark matter is made up of Weakly Interacting Massive Particles, the annihilation of these particles in halos results in energy being released, some of which is absorbed by gas, causing partial ionization and heating. It is shown that early ionization results in a transfer of power to higher multipoles in the large angle CMB polarization power spectra. Future CMB experiments may be able to detect this effect in the case of certain light dark matter models. We also investigate the effect of gas heating on the expected H21 cm power spectrum. Heating by particle annihilation results in a decrease in the amplitude of the H21 cm power spectrum as the gas temperature TT becomes comparable to the CMB temperature TγT_\gamma, and then an increase as T>TγT > T_\gamma. The result is a minimum in the power spectrum at the redshift for which T≈TγT \approx T_\gamma. Only certain models (low particle masses ∼\sim 10 GeV, or favorable halo parameters) show this effect. Within these models, observations of the H21 cm power spectrum at multiple redshifts can help us obtain constraints on particle and halo properties.
  • 95.35.+d
  • polarization: power spectrum
  • WIMP: dark matter
  • cosmic background radiation
  • dark matter: halo
  • luminosity: redshift
  • WIMP: annihilation
  • ionization
  • hydrogen
  • gas: temperature
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