Key points are not available for this paper at this time.
ABSTRACT The origin of the ‘seeds’ of supermassive black holes (BHs) continues to be a puzzle, as it is currently unclear if the imprints of early seed formation could survive to today. We examine the signatures of seeding in the local Universe using five 18~Mpc³BRAHMA simulation boxes run to z=0. They initialize 1. 5 10⁵~ M BHs using different seeding models. The first four boxes initialize BHs as heavy seeds using criteria that depend on dense and metal-poor gas, Lyman–Werner radiation, gas spin, and environmental richness. The fifth box initializes BHs as descendants of lower mass seeds (10³~ M) using a new stochastic seed model built in our previous work. In our simulations, we find that the abundances and properties of 10⁵-10⁶~ M local BHs hosted in M_* 10^9~ M dwarf galaxies, are sensitive to the assumed seeding criteria. This is for two reasons: (1) there is a substantial population of local 10⁵~ M BHs that are ungrown relics of early seeds from z 5-10; (2) BH growth up to 10⁶~ M is dominated by mergers in our simulations all the way down to z 0. As the contribution from gas accretion increases, the signatures of seeding start to weaken in more massive 10⁶~ M BHs, and they are erased for 10⁷~ M BHs. The different seed models explored here predict abundances of local 10⁶~ M BHs ranging from 0. 01-0. 05~Mpc^-3 with occupation fractions of 20-100~{\ per\ cent} for M_* 10^9~ M galaxies. These results highlight the potential for placing constraints on seeding models using local 10⁵-10⁶~ M BHs hosted in dwarf galaxies. Since merger dynamics and accretion physics impact the persistence of seeding signatures, and both high and low mass seed models can produce similar local BH populations, disentangling their roles will require combining high and low redshift constraints.
Bhowmick et al. (Thu,) studied this question.