Hydrogen Mixing as a Novel Mechanism for Colder Baryons in 21 cm Cosmology

Abstract

The anomalous 21 cm absorption feature reported by EDGES has galvanized the study of scenarios in which dark matter (DM) siphons off thermal energy from the Standard Model (SM) gas. In a departure from the much-discussed models that achieve cooling by DM scattering directly with SM particles, we show that the same end can be achieved through neutral atomic hydrogen $H$ mixing with a degenerate dark sector state $H^{\prime }$. An analysis of in-medium $H$-$H^{\prime }$ oscillations reveals viable parameter space for generic types of $H^{\prime }$-DM interactions to provide the requisite cooling. This strategy stands in stark contrast to other proposals in many respects, including its cosmological dynamics, model building implications, and complementary observational signatures.

arXiv comment6 pages, 4 figures

References in corpus (18)

• Sterile Neutrinos as Dark Matter
• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• A census of baryons in the Universe from localized fast radio bursts
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• Constraining Dark Matter-Baryon Scattering with Linear Cosmology
• Observations of the MIssing Baryons in the warm-hot intergalactic medium
• Insights on Dark Matter from Hydrogen during Cosmic Dawn
• Severely Constraining Dark Matter Interpretations of the 21-cm Anomaly
• Signs of Dark Matter at 21-cm?
• Early-Universe Constraints on Dark Matter-Baryon Scattering and their Implications for a Global 21cm Signal
• Tighter Limits on Dark Matter Explanations of the Anomalous EDGES 21cm Signal
• Heating of Baryons due to Scattering with Dark Matter During the Dark Ages
• Reviving Millicharged Dark Matter for 21-cm Cosmology
• The EDGES 21 cm Anomaly and Properties of Dark Matter
• Testing for calibration systematics in the EDGES low-band data using Bayesian model selection
• On the contamination of the global 21~cm signal from polarized foregrounds
• Dark photon portal dark matter with the 21-cm anomaly
• Derivation of the sterile neutrino Boltzmann equation from quantum kinetics

Cited by in corpus (2)

• Cosmological and astrophysical probes of dark baryons
• The Hydrogen Mixing Portal, Its Origins, and Its Cosmological Effects