Speaker
Description
Dense gas in minihalos can shield themselves from reionization for ~100 Myr after being exposed to UV background. These self-shielded systems, often unresolved in cosmological simulations, can introduce strong absorption in quasar spectra. We present the first systematic study on the impact of these systems on the Lya forest. We find that the incidence rate of damped Lya absorbers increases by a factor of ~2 - 4 between z=4.5 and 5.5, and the Lya flux is, on average suppressed by ~3% of its mean due to minihalos. The absorption features enhances the 1D power spectrum by up to ~10 % at k~0.1 h/Mpc. The flux is particularly suppressed in the vicinity of large halos along the line-of-sight direction. However, these effects become much smaller for higher ionizing rates (>~ 10^-12/s) expected in the post-reionization universe. Our findings highlight the need to consider minihalo absorption when interpreting the Lya forest at z>~5.5. Moreover, the sensitivity of this effect to the ionizing background intensity can be exploited to constrain the intensity itself.
