Constraints on Dark Matter-Baryon Scattering from the Temperature Evolution of the Intergalactic Medium

Understand

The thermal evolution of the intergalactic medium (IGM) can serve as a sensitive probe of cosmological heat sources and sinks.

• We employ it to limit interactions between dark matter and baryons.
• After reionization the IGM temperature is set by the balance between photoheating and adiabatic cooling.
• We use measurements of the IGM temperature from Lyman-$\alpha$-forest data to constrain the cross-section $\sigma$ between dark matter and baryons, finding $\sigma < 10^{-20}$ cm$^2$ for dark-matter masses $m_\chi\leq 1$ GeV.