Neutralino Annihilations and the Gas Temperature in the Dark Ages

Abstract

Assuming the dark matter is made entirely from neutralinos, we re-visit the role of their annihilation on the temperature of diffuse gas in the high redshift universe. We consider neutralinos of particle mass 36 GeV and 100 GeV, respectively. The former is able to produce ~7 electron/positron particles per annihilation through the fremionic channel, and the latter ~53 particles assuming a purely bosonic channel. High energy electron/positron particles up-scatter the Cosmic Microwave Background (CMB) photons into higher energies via the inverse-Compton scattering. The process produces a power-law electron/positron energy spectrum of index -1 in the energy range of interest, independent of the initial energy distribution. The corresponding energy spectrum of the up-scattered photons is a power-law of index -1/2, if absorption by the gas is not included. The scattered photons photo-heat the gas by releasing electrons which deposit a fraction (14%)of their energy as heat into the ambient medium. For uniformly distributed neutralinos the heating is insignificant. The effect is greatly enhanced by the clumping of neutralinos into dense haloes. We use a time-dependent clumping model which takes into account the damping of density fluctuations on mass scales smaller than ~10^{-6}M_sol. With this clumping model, the heating mechanism boosts the gas temperature above that of the CMB after a redshift of z 30. By z\approx 10 the gas temperature is nearly 100 times its temperature when no heating is invoked. Similar increase is obtained for the two neutralino masses considered.

8 pages, 6 figures, submitted to MNRAS

References in corpus (7)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Impact of dark matter decays and annihilations on reionization
• The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
• The impacts of dark matter particle annihilation on recombination and the anisotropies of the cosmic microwave background
• Time-evolution of ionization and heating around first stars and miniquasars
• Intergalactic medium heating by dark matter
• 511 keV line and diffuse gamma rays from moduli

Cited by in corpus (6)

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• Impact of Dark Matter Annihilation on the High-Redshift Intergalactic Medium
• HI absorption from the epoch of reionization and primordial magnetic fields
• SUSY dark matter annihilation in the Galactic halo