Lux ex tenebris: The imprint of annihilating dark matter on the intergalactic medium during Cosmic Dawn

Abstract

Upcoming measurements of the highly redshifted 21cm line with next-generation radio telescopes such as HERA and SKA will provide the intriguing opportunity to probe dark matter (DM) physics during the Epoch of Reionization (EoR), Cosmic Dawn, and the Dark Ages. With HERA already under construction, there is a pressing need to thoroughly understand the impact of DM physics on the intergalactic medium (IGM) during these epochs. We present first results of a hydrodynamic simulation suite with 2 × 512 3 particles in a (100 h −1 Mpc) 3 box with DM annihilation and baryonic cooling physics. We focus on redshift z ∼ 11, just before reionization starts in our simulations, and discuss the imprint of DM annihilation on the IGM and on structure formation. We find that whereas structure formation is not affected by thermal WIMPs heavier than m χ 100 MeV, heating from O(GeV) DM particles may leave a significant imprint on the IGM that alters the 21cm signal. Cold gas in low density regions is particularly susceptible to the effects of DM heating. We note, however, that delayed energy deposition is not currently accounted for in our simulations.

Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn

“…The 21-cm signal at cosmic dawn is a promising probe for studying alternative dark matter (DM) scenarios. It is particularly sensitive to DM decays or annihilation [4][5][6], interactions between DM and standard model particles [7,8], or DM models yielding a suppression of the smallscale matter power spectrum [9][10][11][12][13][14]. While decay and annihilation scenarios provide additional sources of radiation that may affect the 21-cm signal, interacting DM models can lead to additional cooling channels, acting on the temperature and the distribution of the gas.…”