Speaker
Description
It has been noted recently that the latest JWST observations at z > 6 may suggest ionizing photon production by galaxies significantly in excess of previous expectations. Taken at face value, this apparent excess implies an earlier end to reionization (at z ~ 8) than suggested by measurements of the CMB optical depth and especially the 5 < z < 6 Ly-alpha forest. There are two viable avenues for re-establishing agreement with forest observations, both of which require reionization to end at z < 6. Either reionization began relatively late (at z ~ 8-9), proceeded rapidly, or it began early (z > 12) and ended gradually. I will discuss the implications of these two scenarios for the evolution of the ionizing properties of galaxies, in light of the latest measurements of the UV luminosity function from JWST. I will also explore the concordance of these models with QSO observations at 5 < z < 6 and observations of bright Ly-alpha emitters at z > 8, with a focus on whether the late-starting model can explain the latter. If there is time, I will highlight recent developments in my work to improve the efficiency and accuracy of reionization simulations. These include a new suite of multi-scale, high-resolution hydro/RT simulations of IGM gas dynamics spanning a wide parameter space of large-scale IGM environments and reaching sub-kpc resolution. These simulations will allow for a sub-grid treatment of the IGM in reionization simulations with volumes up to 1 Gpc^3 with 7 orders of magnitude of dynamic range in the IGM opacity.
