Hidden Sector Hydrogen as Dark Matter: Small-scale Structure Formation Predictions and the Importance of Hyperfine Interactions

Abstract

We study the atomic physics and the astrophysical implications of a model in which the dark matter is the analog of hydrogen in a secluded sector. The self interactions between dark matter particles include both elastic scatterings as well as inelastic processes due to a hyperfine transition. The self-interaction cross sections are computed by numerically solving the coupled Schrödinger equations for this system. We show that these self interactions exhibit the right velocity dependence to explain the low dark matter density cores seen in small galaxies while being consistent with all constraints from observations of clusters of galaxies. For a viable solution, the dark hydrogen mass has to be in 10--100 GeV range and the dark fine-structure constant has to be larger than 0.02. Precisely for this range of parameters, we show that significant cooling losses may occur due to inelastic excitations to the hyperfine state and subsequent decays, with implications for the evolution of low-mass halos and the early growth of supermassive black holes. Cooling from excitations to higher $n$ levels of dark hydrogen and subsequent decays is possible at the cluster scale, with a strong dependence on halo mass. Finally, we show that the minimum halo mass is in the range of $10^{3.5}$ to $10^7{M}_{\odot }$ for the viable regions of parameter space, significantly larger than the typical predictions for weakly-interacting dark matter models. This pattern of observables in cosmological structure formation is unique to this model, making it possible to rule in or rule out hidden sector hydrogen as a viable dark matter model.

22 pages, 6 figures, 2 tables; v2: published version

References in corpus (10)

• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• High-Resolution Rotation Curves and Galaxy Mass Models from THINGS
• Precise Relic WIMP Abundance and its Impact on Searches for Dark Matter Annihilation
• The non-gravitational interactions of dark matter in colliding galaxy clusters
• The First Galaxies: Assembly, Cooling and the Onset of Turbulence
• Is there a "too big to fail" problem in the field?
• Effects of cold dark matter decoupling and pair annihilation on cosmological perturbations
• Supermassive Black Holes from Ultra-Strongly Self-Interacting Dark Matter
• Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics
• 3.5 keV X-rays as the "21 cm line" of dark atoms, and a link to light sterile neutrinos

Cited by in corpus (5)

• Cosmic particle colliders: simulations of self-interacting dark matter with anisotropic scattering
• Dynamical Dark Matter from Strongly-Coupled Dark Sectors
• Self-interacting inelastic dark matter: A viable solution to the small scale structure problems
• Cooling in a Dissipative Dark Sector
• Updated Constraints on Self-Interacting Dark Matter from Supernova 1987A