Cosmological 21cm line observations to test scenarios of superEddington accretion on to black holes being seeds of highredshifted supermassive black holes
Abstract
In this paper we study scenarios of the superEddington accretion onto black holes at high redshifts z >10 , which are expected to be seeds to evolve to supermassive black holes until redshift z ∼7 . For a initial mass, M_{BH ,ini}≲2 ×10^{3} M_{⊙} of a seed black hole (BH), we definitely need the superEddington accretion, which can be applicable to both astrophysical and primordial origins. Such an accretion disk inevitably emitted highenergy photons which had heated the cosmological plasma of the intergalactic medium continuously from high redshifts. In this case, cosmic history of cosmological gas temperature is modified, by which the absorption feature of the cosmological 21cm lines are suppressed. By comparing theoretical predictions of the 21cm line absorption with the observational data at z ∼17 , we obtain a cosmological upper bound on the massaccretion rate as a function of the seed BH masses. In order to realize M_{BH}∼10^{9} M_{⊙} at z ∼7 by a continuous mass accretion on to a seed BH, to be consistent with the cosmological 21cm line absorption at z ∼17 , we obtained an severe upper bound on the initial mass of the seed BH to be M_{BH ,ini}≲10^{2} M_{⊙} (M_{BH ,ini}≲10^{6} M_{⊙} ) when we assume a seed BH with its comoving number density n_{seed ,0}∼10^{3} Mpc^{3} (n_{seed ,0}∼10^{7} Mpc^{3} ). We also discuss some implications for application to primordial black holes as the seed black holes.
 Publication:

Physical Review D
 Pub Date:
 August 2022
 DOI:
 10.1103/PhysRevD.106.043539
 arXiv:
 arXiv:2201.05300
 Bibcode:
 2022PhRvD.106d3539K
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 13 pages, 8 figures, to appear in Phys. Rev. D