In the Simulations and Constructions of the Reionization of Cosmic Hydrogen ( SCORCH ) project , we present new radiation-hydrodynamic simulations with updated high-redshift galaxy populations and varying radiation escape fractions .
The simulations are designed to have fixed Thomson optical depth \tau \approx 0.06 , consistent with recent Planck observations , and similar midpoints of reionization 7.5 \lesssim z \lesssim 8.0 , but with different ionization histories .
The galaxy luminosity functions and ionizing photon production rates in our model are in good agreement with recent HST observations .
Adopting a power-law form for the radiation escape fraction f _ { \text { esc } } ( z ) = f _ { 8 } [ ( 1 + z ) / 9 ] ^ { a _ { 8 } } , we simulate the cases for a _ { 8 } = 0 , 1 , and 2 and find a _ { 8 } \lesssim 2 in order to end reionization in the range 5.5 \lesssim z \lesssim 6.5 to be consistent with Lyman alpha forest observations .
At fixed \tau and as the power-law slope a _ { 8 } increases , the reionization process starts earlier but ends later with a longer duration \Delta z and the decreased redshift asymmetry Az .
We find a range of durations 3.9 \lesssim \Delta z \lesssim 4.6 that is currently in tension with the upper limit \Delta z < 2.8 inferred from a recent joint analysis of Planck and South Pole Telescope observations .