BLUETIDES simulation: Establishing black hole-galaxy relations at high redshift

Abstract

The scaling relations between the mass of supermassive black holes (M•) and host galaxy properties (stellar mass, M*, and velocity dispersion, s) provide a link between the growth of black holes (BHs) and that of their hosts. Here we investigate if and how the BH-galaxy relations are established in the high-z Universe using BLUETIDES, a high-resolution large volume cosmological hydrodynamic simulation. We find the M•-M* and M•-σ relations at z = 8: log10(M•) = 8.25 + 1.10 log10(M*/1011M⊙) and log10(M•) = 8.35 + 5.31 log10(s/200 km s-1) at z = 8, both fully consistent with the local measurements. The slope of the M•-σ relation is slightly steeper for high star formation rate and M* galaxies while it remains unchanged as a function of Eddington accretion rate on to the BH. The intrinsic scatter in M•-σ relation in all cases (ε ~ 0.4) is larger at these redshifts than inferred from observations and larger than in M•-M* relation (ε ~ 0.14). We find the gas-to-stellar ratio f = Mgas/M* in the host (which can be very high at these redshifts) to have the most significant impact setting the intrinsic scatter of M•-σ. The scatter is significantly reduced when galaxies with high gas fractions (ε = 0.28 as f < 10) are excluded (making the sample more comparable to low-z galaxies); these systems have the largest star formation rates and BH accretion rates, indicating that these fast-growing systems are still moving towards the relation at these high redshifts. Examining the evolution (from z= 10 to 8) of high-mass BHs in M•-σ plane confirms this trend.