Recent observations of quasars powered by supermassive black holes ( SMBHs ) out to z \gtrsim 7 constrain both the initial seed masses and the growth of the most massive black holes ( BHs ) in the early universe .
Here we elucidate the implications of the radiative feedback from early generations of stars and from BH accretion for popular models for the formation and growth of seed BHs .
We show that by properly accounting for ( 1 ) the limited role of mergers in growing seed BHs as inferred from cosmological simulations of early star formation and radiative feedback , ( 2 ) the sub-Eddington accretion rates of BHs expected at the earliest times , and ( 3 ) the large radiative efficiencies \epsilon of the most massive BHs inferred from observations of active galactic nuclei at high redshift ( \epsilon \gtrsim 0.1 ) , we are led to the conclusion that the initial BH seeds may have been as massive as \gtrsim 10 ^ { 5 } M _ { \odot } .
This presents a strong challenge to the Population III seed model , which calls for seed masses of \sim 100 M _ { \odot } and , even with constant Eddington-limited accretion , requires \epsilon \lesssim 0.09 to explain the highest- z SMBHs in today ’ s standard \Lambda CDM cosmological model .
It is , however , consistent with the prediction of the direct collapse scenario of SMBH seed formation , in which a supermassive primordial star forms in a region of the universe with a high molecule-dissociating background radiation field , and collapses directly into a 10 ^ { 4 } – 10 ^ { 6 } M _ { \odot } seed BH .
These results corroborate recent cosmological simulations and observational campaigns which suggest that these massive BHs were the seeds of a large fraction of the SMBHs residing in the centers of galaxies today .