Flowchart visualizing the method we use to model the reionization of hydrogen and helium accounting for ionizing radiation from stellar populations and AGN. The quantities that we consider uncertain are written in red. See Sect. 2 for details and also, e.g., Madau et al. (1999) and Haardt & Madau (2012) where similar methods have been employed. (The massive stars in STARBURST99 are represented by evolutionary models from the Geneva grids (Ekström et al. 2012; Levesque et al. 2012; Georgy et al. 2013), atmosphere models from CMFGEN for Wolf-Rayet stars (Hillier & Miller 1998; Smith et al. 2002), and atmosphere models from WM-BASIC for OB-stars (Pauldrach et al. 2001; Leitherer et al. 2010).)