The descendants of the first quasars in the BlueTides simulation

TL;DR

This study uses the BlueTides simulation to trace the evolution of early quasars' descendants, revealing they typically inhabit group-sized halos and are not among the most massive black holes in present-day massive clusters.

Contribution

It provides new insights into the environments and black hole masses of descendants of first quasars at low redshift using a dark matter-only realization of the BlueTides simulation.

Findings

Descendants of early quasars are found in group-sized halos (~10^14 M_sun).

Most massive halos at z=0 do not host the most massive black holes from z=8.

Low probability (20%) of high-redshift quasars with >10^7 M_sun black holes in halos >10^15 M_sun.

Abstract

Supermassive blackholes with masses of a billion solar masses or more are known to exist up to $z=7$. However, the present-day environments of the descendants of first quasars is not well understood and it is not known if they live in massive galaxy clusters or more isolated galaxies at $z=0$. We use a dark matter-only realization (BTMassTracer) of the BlueTides cosmological hydrodynamic simulation to study the halo properties of the descendants of the most massive black holes at $z=8$. We find that the descendants of the quasars with most massive black holes are not amongst the most massive halos. They reside in halos of with group-like ($\sim 10^{14}M_{\odot}$) masses, while the most massive halos in the simulations are rich clusters with masses $\sim 10^{15} M_{\odot}$. The distribution of halo masses at low redshift is similar to that of the descendants of least massive black holes, for a similar range of halo masses at $z=8$, which indicates that they are likely to exist in similar environments. By tracing back to the $z = 8$ progenitors of the most massive (cluster sized) halos at $z=0$; we find that their most likely black hole mass is less than $10^7 M_{\odot}$; they are clearly not amongst the most massive black holes. We also provide estimates for the likelihood of finding a high redshift quasar hosting a black hole with masses above $10^{7} M_{\odot}$ for a given halo mass at $z=0$. For halos above $10^{15} M_{\odot}$, there is only $20 \%$ probability that their $z=8$ progenitors hosted a black hole with mass above $10^{7} M_{\odot}$.