We examine the properties of the host galaxies of z = 7 quasars using the large volume , cosmological hydrodynamical simulation BlueTides .
We find that the most massive black holes and quasars are hosted by massive galaxies with stellar masses \log ( M _ { \ast } / M _ { \odot } ) = 10.8 \pm 0.2 , and 10.2 \pm 0.4 , which have a wide range of star formation rates , of 50 \substack { +119 \ -35 } M _ { \odot } / yr and 19 \substack { +28 \ -12 } M _ { \odot } / yr , respectively .
The hosts of the most massive black holes and quasars in BlueTides are generally bulge-dominated , with bulge-to-total mass ratio B / T \simeq 0.85 \pm 0.1 , however their morphologies are not biased relative to the overall z = 7 galaxy sample .
We find that the hosts of the most massive black holes and quasars are significantly more compact , with half-mass radii R _ { 0.5 } = 0.29 \substack { +0.15 \ -0.10 } kpc and 0.28 \substack { +0.08 \ -0.06 } kpc respectively , relative to galaxies with similar masses , which have R _ { 0.5 } = 0.5 \substack { +0.3 \ -0.2 } kpc .
We make mock James Webb Space Telescope ( JWST ) images of these quasars and their host galaxies .
We find that distinguishing the host from the quasar emission will be possible but still challenging with JWST , due to the small sizes of quasar hosts .
We find that currently observable quasar samples are biased tracers of the intrinsic black hole–stellar mass relations , following a relation that is 0.27 dex higher than that of the full galaxy sample .
Finally , we find that black hole hosts are generally quite isolated .
However , the most massive black holes are more likely to be found in denser environments than the typical M _ { \textrm { BH } } > 10 ^ { 6.5 } M _ { \odot } black hole , indicating that minor mergers at least play some role in growing black holes in the early Universe .