Escape fraction catalogs

For all snapshots we produce ionizing escape fraction catalogs directly mirroring the SUBFIND subhalo catalogs. These post-processing files provide supplemental data for each subhalo with at least one star particle and four gas cells within the virial radius, corresponding to identifications of dark matter halos. There is a single HDF5 file for each snapshot named ion_[file].hdf5 containing simulation attributes and subhalo datasets. Full details are given in Section 2 of Yeh et al. (2022).

We calculate the radius \(R_{\rm 200}\) at which the average density reaches 200 times the density of the universe, and adopt this same definition for the halo mass \(M_{\rm halo}\), stellar mass \(M_{\rm stars}\), instantaneous star-formation rate (SFR), and other quantities. This ensures a consistent accounting of properties contributing to the escape fraction, which we define as the ratio between the number of ionizing photons that escape and are intrinsically emitted from all sources within the virial radius, i.e. $$f_{\rm esc} \equiv \dot{N}_{\rm esc} / \dot{N}_{\rm int} \, .$$ The escape fractions for star particles outside the virial radius of any halo are assumed to be maximal (i.e. the birth cloud value \(f_{\rm esc}^{\rm cloud}\)) as these directly contribute to reionizing the IGM. The intrinsic photon rate for each subhalo (including stars outside \(R_{200}\) is provided in the Lyα emission catalog (Subhalo_NoSFR HDF5 group) described in Smith et al. (2022a), which is calculated from the Binary Population and Spectral Synthesis models (BPASS version 2.2.1; Eldridge et al. 2017) with a Chabrier initial mass function (IMF; Chabrier 2003). Passive Monte Carlo radiative transfer (MCRT) calculations were performed with the Cosmic Lyα Transfer (colt) code, with the details of the photo-ionization physics and MCRT implementation most recently described in Smith et al. (2022b).