Speaker
Mrs
Anna Schauer
(Universität Heidelberg)
Description
Population III (or Pop III) stars can influence their surroundings in several ways and by so doing regulate subsequent star formation. Their radiation may ionize or photodissociate H2 in the surrounding interstellar medium and break out to affect other halos. Even if ionizing photons are trapped, Lyman-Werner (LW) photons may still escape the halo and photodissociate H2 in nearby halos, preventing them from cooling and forming stars. The LW escape fraction therefore is a key parameter in cosmological simulations of early reionization and star formation. Its value for realistic high-redshift halos has not yet been parametrized as function of halo mass or stellar mass. To do so, we have performed radiation hydrodynamical simulations of LW UV escape from 10^5 to 10^7 Msol halos with 9 - 120 Msol Pop III stars with the ZEUS-MP code. We find that escape fractions vary from 0% to 95%, depending on halo and stellar mass, and that LW photons cannot escape the most massive halo locally in our sample even from the most massive Pop III star. We also find that shielding of H2 by neutral hydrogen, which has been neglected in simulations to date, produces escape fractions that are considerably lower, up to factors of three for the least massive stars in our sample, than those predicted by H2 self-shielding alone.
Author
Mrs
Anna Schauer
(Universität Heidelberg)