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SUMMARY:Probing the Post to Early Stage of Cosmic Reionization using JWST 
 and Subaru - Hiroya Umeda (Tokyo)
DTSTART:20241011T103000Z
DTEND:20241011T113000Z
UID:TALK220000@talks.cam.ac.uk
CONTACT:Sandro Tacchella
DESCRIPTION:Lya damping wing absorption measurement is a useful tool to co
 nstrain the key cosmic reionization parameters including neutral hydrogen 
 fraction xHI\, but the measurement had been limited only to the small numb
 er of extremely UV-continuum bright sources such as QSO/GRBs. For the firs
 t time\, we constrain xHI and ionized bubble radii Rb by measuring Lya dam
 ping wing absorptions using bright galaxy spectra detected in JWST observa
 tions. We combine JWST/NIRSpec spectra taken by CEERS\, GO-1433\, DDT-2750
 \, and JADES programs\, and obtain 27 bright (M_UV<-18.5) UV-continuum gal
 axies at 7 < z < 12. We construct 4 composite spectra binned by redshift a
 nd find the clear transition from sharp to soft spectral break towards hig
 h redshift at the restframe 1216 Å suggesting the increase of Lyα dampin
 g wing absorption. We estimate Lya damping wing absorption in the galaxy s
 pectra with a state-of-art stellar population synthesis model including Ly
 a emission and host HI absorptions. Assuming the standard inside-out reion
 ization picture having an ionized bubble with Rb around a galaxy in the in
 tergalactic medium of xHI\, we obtain xHI (Rb) values monotonically increa
 sing (decreasing) trend from xHI = 0.54 to 0.95 (log Rb = 1.89 to -0.68 co
 moving Mpc) at redshift 7.12 to 9.91. We also estimate xHI at z<7 using th
 e largest Lya emitter (LAE) catalog from Subaru Hyper Suprime-Cam photomet
 ric survey constructed by Kikuta et al. (2023). The z>5.7 Subaru LAE catal
 og consists of 8182 galaxies\, and we estimate xHI from Lya luminosity fun
 ction and LAE clustering properties using a prediction based on semi-numer
 ical simulation 21cmFAST. The redshift evolution of xHI between z=6 to 12 
 inferred from JWST and Subaru result indicate a very rapid reionization sc
 enario progressing mainly at z=7-8.\n
LOCATION:Ryle Seminar Room\, KICC + online
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