Probing cosmic reionization with Ly alpha observations from JWST/NIRSpec


The JWST is ushering in a new era of observing galaxies in the reionization era, providing us new insights into this last major phase transition of the Universe. The Ly-alpha emission from young star forming galaxies, which is sensitive to the presence of neutral HI along the line of sight, has been used as an important probe of the reionization process. JWST/NIRSpec offers spectroscopic capabilities that allow for efficient detections of z>~6 Ly-alpha emission lines in the absence of atmospheric OH lines down to very faint continuum magnitudes (~ 29 mag). In this talk, I will present our recent work using NIRSpec observations to directly constrain the reionization timeline by measuring the Ly alpha escape fractions. I will show the detection of extremely strong Ly alpha in z>7 galaxies, and its implications for the presence of large ionized bubbles when the universe is significantly neutral. Lastly, I will discuss how Ly alpha visibility in early galaxies may depend on their local environments and what we learned for future Ly alpha observations.

Zuyi Chen (陈祖诒), Steward Observatory, University of Arizona
KIAA Shu Qi meeting room
Friday, June 28, 2024 - 1:30PM to Friday, June 28, 2024 - 2:30PM