A tiny host galaxy for the first giant black hole: $z= 7.5$ quasar in
  BlueTides
  The most distant known quasar recently discovered by Ba\~nados et al. (2018)
is at $z=7.5$ (690 Myr after the Big Bang), at the dawn of galaxy formation. We
explore the host galaxy of the brightest quasar in the large volume
cosmological hydrodynamic simulation BlueTides, which in Phase II has reached
these redshifts. The brightest quasar in BlueTides has a luminosity of a $\sim$
few $10^{13} L_{\odot}$ and a black hole mass of $6.4 \times 10^{8} M_{\odot}$
at $z \sim 7.5$, comparable to the observed quasar (the only one in this large
volume). The quasar resides in a rare halo of mass $M_{H} \sim 10^{12}
M_{\odot}$ and has a host galaxy of stellar mass of $4 \times 10^{10}M_{\odot}$
with an ongoing (intrinsic) star formation rate of $\sim 80 M_{\odot} yr^{-1}$.
The corresponding intrinsic UV magnitude of the galaxy is $-23.1$, which is
roughly $2.7$ magnitudes fainter than the quasar's magnitude of $-25.9$. We
find that the galaxy is highly metal enriched with a mean metallicity equal to
the solar value. We derive quasar and galaxy spectral energy distribution (SED)
in the mid and near infrared JWST bands. We predict a significant amount of
dust attenuation in the rest-frame UV corresponding to $A_{1500} \sim 1.7$
giving an UV based SFR of $\sim 14 M_{\odot} yr^{-1}$. We present mock JWST
images of the galaxy with and without central point source, in different MIRI
and NIRCam filters. The host galaxy is detectable in NIRCam filters, but it is
extremely compact ($R_{E}=0.35$ kpc). It will require JWST's exquisite
sensitivity and resolution to separate the galaxy from the central point
source. Finally within the FOV of the quasar in BlueTides there are two more
sources that would be detectable by JWST.
