Photoionization heating
= Photoionization heating
= Photoheating
{synonym}
Absorption of an ionizing photon leaves energy in a photoelectron above the binding energy. Thermalization supplies heat to the gas. <Photoionization heating> competes with the <astrophysical cooling function>, can establish thermal equilibrium, and can raise the pressure enough to inhibit baryon accretion into shallow <dark-matter haloes>.