A fresh look into the interacting dark matter scenario

Abstract

The elastic scattering between dark matter particles and radiation represents an attractive possibility to solve a number of discrepancies between observations and standard cold dark matter predictions, as the induced collisional damping would imply a suppression of small-scale structures. We consider this scenario and confront it with measurements of the ionization history of the Universe at several redshifts and with recent estimates of the counts of Milky Way satellite galaxies. We derive a conservative upper bound on the dark matterphoton elastic scattering cross section of σ γDM < 8×10 −10 σ T (m DM /GeV) at 95% CL, about one order of magnitude tighter than previous constraints from satellite number counts. Due to the strong degeneracies with astrophysical parameters, the bound on the dark matter-photon scattering cross section derived here is driven by the estimate of the number of Milky Way satellite galaxies. Finally, we also argue that future 21 cm probes could help in disentangling among possible non-cold dark matter candidates, such as interacting and warm dark matter scenarios. Let us emphasize that bounds of similar magnitude to the ones obtained here could be also derived for models with dark matter-neutrino interactions and would be as constraining as the tightest limits on such scenarios.

Neutrino portals to dark matter

“…This effect leads to a suppression of the amount of small scale structures today. By comparing LSS predictions to observations, one can set an upper bound on the strength of the elastic scattering between DM and neutrinos [8,78]. Nevertheless, for the models we are presenting in this work, the mixing between the sterile and SM neutrino suppresses the neutrino-DM elastic scattering and, consequently, its effect on LSS constrains regions of the parameter space already ruled out by CMB and BBN constraints [14].…”

Dark matter microphysics and 21 cm observations

“…[43,44,58,59]. As a result a shift to later times in the typical features in the 21 cm sky-averaged global signal and power spectrum is observed in the context of non-cold dark matter [58,59,[77][78][79]. Consequently, it is timely to study the compatibility between the observation reported by EDGES, located at a redshift around z 17 and the IDM scenario.…”

“…While NCDM scenarios are unlikely to explain the large absorption amplitude, they delay structure formation and, therefore, might delay the onset of reionization and of UV and X-ray emission, see e.g. [43,44,58,59]. As a result a shift to later times in the typical features in the 21 cm sky-averaged global signal and power spectrum is observed in the context of non-cold dark matter [58,59,[77][78][79].…”

Probing the small-scale matter power spectrum with large-scale 21-cm data

“…Previous works have studied the effect of non-CDM models on the 21-cm signal [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Those models typically suppress the matter power spectrum beyond some wavenumber k, delaying the onset of cosmic dawn.…”