Number density of hydrogen nuclei, temperature, and escape fraction of
line photons in the central
of a minihalo, shown for various treatments of the optically thick
line cooling rate. The top row shows the outcome for the density-dependent fit of Ripamonti and Abel (2004), the middle row for the Sobolov method, and the bottom row for the self-consistent radiative transfer calculation of Greif (2014). The Sobolev method greatly overestimates the escape fraction at high densities, whereas the fitting function shows better agreement with the ray-tracing solution, even though the gas fragments in this particular simulation. Adapted from Greif (2014).