Effects of binary stellar populations on direct collapse black hole
  formation
  The critical Lyman--Werner flux required for direct collapse blackholes
(DCBH) formation, or J$_{crit}$, depends on the shape of the irradiating
spectral energy distribution (SED). The SEDs employed thus far have been
representative of {{realistic}} single stellar populations. We study the effect
of binary stellar populations on the formation of DCBH, as a result of their
contribution to the Lyman--Werner radiation field. Although binary populations
with ages $>$ 10 Myr yield a larger LW photon output, we find that the
corresponding values of J$_{crit}$ can be up to 100 times higher than single
stellar populations. We attribute this to the shape of the binary SEDs as they
produce a sub--critical rate of H$^-$ photodetaching 0.76 eV photons as
compared to single stellar populations, reaffirming the role that H$^-$ plays
in DCBH formation. This further corroborates the idea that DCBH formation is
better understood in terms of a critical region in the H$_2$--H$^-$
photo--destruction rate parameter space, rather than a single value of LW flux.
