Cosmic Reionization History and Dark Matter Scenarios
  We perform an analysis of the cosmic reionization in the standard cold dark
matter (CDM) paradigm and in alternative dark matter scenarios. Building upon
the work of Corasaniti et al. (2017), we predict the reionization history for
CDM, for warm dark matter (WDM), late-forming dark matter (LFDM) and
ultra-light axion dark matter (ADM) models which reproduce state-of-art
measurements of the galaxy luminosity function at very high-redshifts $6\le
z\le 10$. To this purpose we adopt a reionization model parametrized in terms
of the limiting UV-magnitude of galaxies contributing to the reionization
$M_{\rm lim}$ and the average effective escape fraction of UV photons reaching
the intergalactic medium $\tilde{f}$. For each DM model we compute the redshift
evolution of the Thomson scattering optical depth $\tau_e(z)$ and the comoving
ionization fraction $Q_{\rm HII}(z)$. We find the different DM models to have
similar reionization histories. Differences with respect to the CDM case
increase at fainter limiting UV-magnitudes and are degenerate with the effect
of varying the reionization model parameters. Using Planck's determination of
the integrated optical depth in combination with measurements of the neutral
hydrogen fraction at different redshifts, we infer constraints on $\tilde{f}$
and $M_{\rm lim}$. The results are largely independent of the assumed DM
scenario, in particular for $M_{\rm lim}\gtrsim -13$ we obtain that the
effective escape fraction lies in the range $0.07\lesssim \tilde{f}\lesssim
0.15$ at $2\sigma$.
