Speaker
Description
Direct collapse black hole formation with the mass of 10^5 Msun is a promising scenario for the origin of high-redshift supermassive black holes. It has usually been supposed that the massive seeds can only form in the primordial gas since the metal enrichment enhances the cooling ability and causes the fragmentation. What actually happens in such an environment, however, has not been explored. We study the impact of the metal enrichment on the clouds, conducting radiation hydrodynamical simulations to follow the cloud evolution in cases with different metallicity environments with Z/Z_sun = 10^-6 to 10^-2. Below Z/Z_sun = 10^-3, although dust cooling promotes fragmentation of the cloud core and produces a number of low-mass stars, the accreting flow preferentially feeds the gas to the central massive stars, which grows supermassive as in the primordial case. When Z/Z_sun = 10^-2, the radiation feedback from the protostars hinders the mass accretion and the final mass is below several 100 Msun.
Supermassive star formation in the metal-enriched environments opens up a new window for seed BHs, which relaxes the condition on metallicity and enhances the seed BH abundance.
