Identifying Direct Collapse Black Hole Seeds through their Small Host
  Galaxies
  Observations of high-redshift quasars indicate that super massive black holes
(SMBHs) with masses greater than ${\sim}10^9~M_\odot$ were assembled within the
first billion years after the Big Bang. It is unclear how such massive black
holes formed so early. One possible explanation is that these SMBHs were seeded
by `heavy' direct collapse black holes (DCBHs) with masses of $M_{\rm
BH}\approx10^5~M_\odot$, but observations have not yet confirmed or refuted
this scenario. In this Letter, we utilize a cosmological N-body simulation to
demonstrate that before they grow roughly an order of magnitude in mass, DCBHs
will have black hole mass to halo mass ratios much higher than expected for
black hole remnants of Population III (Pop III) stars which have grown to the
same mass (${\sim}10^6~M_\odot$). We also show that when $T_{\rm vir}\approx
10^4~{\rm K}$ halos (the potential sites of DCBH formation) merge with much
larger nearby halos ($M_{\rm h} > 10^{10}~M_\odot$), they almost always orbit
their larger host halos with a separation of a few kpc, which is sufficient to
be spatially resolved with future X-ray and infrared telescopes. Thus, we
propose that a future X-ray mission such as Lynx combined with infrared
observations will be able to distinguish high-redshift DCBHs from smaller black
hole seeds due to the unusually high black hole mass to stellar mass ratios of
the faintest observed quasars, with inferred BH masses below ${\sim} 10^6
M_\odot$.
