Binary Stars Can Provide the "Missing Photons" Needed for Reionization

Understand

Empirical constraints on reionization require galactic ionizing photon escape fractions fesc>20%, but recent high-resolution radiation-hydrodynamic calculations have consistently found much lower values ~1-5%.

• While these models include strong stellar feedback and additional processes such as runaway stars, they almost exclusively consider stellar evolution models based on single (isolated) stars, despite the fact that most massive stars are in binaries.
• We re-visit these calculations, combining radiative transfer and high-resolution cosmological simulations from the Feedback in Realistic Environments (FIRE) project.
• For the first time, we use a stellar evolution model that includes a physically and observationally motivated treatment of binaries (the BPASS model).