Photon underproduction crisis: Are QSOs sufficient to resolve it?
  We investigate the recent claim of 'photon underproduction crisis' by
Kollmeier et al. (2014) which suggests that the known sources of ultra-violet
(UV) radiation may not be sufficient to generate the inferred hydrogen
photoionization rate ($\Gamma_{\rm HI}$) in the low redshift inter-galactic
medium. Using the updated QSO emissivities from the recent studies and our
cosmological radiative transfer code developed to estimate the UV background,
we show that the QSO contribution to $\Gamma_{\rm HI}$ is higher by a factor ~2
as compared to the previous estimates. Using self-consistently computed
combinations of star formation rate density and dust attenuation, we show that
a typical UV escape fraction of 4% from star forming galaxies should be
sufficient to explain the inferred $\Gamma_{\rm HI}$ by Kollmeier et al.
(2014). Interestingly, we find that the contribution from QSOs alone can
explain the recently inferred $\Gamma_{\rm HI}$ by Shull et al. (2015) which
used the same observational data but different simulation. Therefore, we
conclude that the crisis is not as severe as it was perceived before and there
seems no need to look for alternate explanations such as low luminosity hidden
QSOs or decaying dark matter particles.
