Café-Club, Hiroya UMEDA: “Cosmic reionization sources and history probed with large galaxy surveys and photoionization modeling”.

Hiroya UMEDA (Institute for Cosmic Ray Research, University of Tokyo): “Cosmic reionization sources and history probed with large galaxy surveys and photoionization modeling”.

You can find the schedule of upcoming café-clubs and the video of old ones here.

Take care,
Carlo, Meriam, Mathilde

—————-
ABSTRACT

Cosmic reionization scenarios are explored by investigating cosmic reionization history and sources from galaxy observations with Subaru telescope. We first consider the possibility of contributions from high energy photons from young galaxies suggested by the detection of strong high-ionization line (e.g., HeII), which are notoriously hard to reproduce with normal stellar populations. We investigated the general ionizing spectrum shapes for the young galaxies using photoionization modeling to explain high ionization lines with other major emission lines. We confirmed that hard power-law like emission explains HeII/Hb flux consistently with other emission line ratios. We also investigated the origin of the hard sources and the contributions to cosmic reionization. We will also present our on-going work on high-z Lya emitters with Subaru/Hyper Suprime Cam to constrain neutral hydrogen fraction evolution at z>6. I also present some on-going efforts on the massive spectroscopy of LAEs with Subaru/Prime Focus Spectrograph (PFS) and future prospects on the synergy with 21cm observations. At last, I would like to discuss the possible science with upcoming instruments such as ROMAN and Subaru/ULTIMATE.