HI photoionization rate at z<0.5 for 79 QSOs

We obtained the HI column density distribution function (CDDF) and linewidth (b) parameter distribution for z<0.45 using spectra of 82 QSOs obtained using the Cosmic Origins Spectrograph and VIPER. The consistency of these with existing measurements in the literature validates our code.

By comparing this CDDF with those obtained from hydrodynamical simulations, we constrain the H I photoionization rate ({Gamma}_HI_) at z<0.45 in four redshift bins. VIPER, together with the Code for Ionization and Temperature Evolution (CITE), which we developed for GADGET-2, allows us to explore parameter space and perform {chi}^2^ minimization to obtain {Gamma}_HI_. We notice that the b parameters from the simulations are smaller than those derived from observations.