SILVERRUSH. VII. Subaru/HSC Identifications of Protocluster Candidates at z ∼ 6–7: Implications for Cosmic Reionization
Inoue, Akio K.
AffiliationUniv Arizona, Steward Observ
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PublisherIOP PUBLISHING LTD
CitationHiguchi, R., Ouchi, M., Ono, Y., Shibuya, T., Toshikawa, J., Harikane, Y., ... & Overzier, R. (2019). SILVERRUSH. VII. Subaru/HSC Identifications of Protocluster Candidates at z∼ 6–7: Implications for Cosmic Reionization. The Astrophysical Journal, 879(1), 28.
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AbstractWe report 14 and 26 protocluster candidates at z = 5.7 and 6.6 over 14 and 16 deg(2) areas, respectively, selected from 2230 (259) Ly alpha emitters (LAEs) photometrically (spectroscopically) identified using Subaru/Hyper Suprime-Cam (HSC) deep images (Keck, Subaru, and Magellan spectra, and literature data). Six out of the 40 protocluster candidates include one to 13 spectroscopically confirmed LAEs. We conduct Monte Carlo simulations to estimate how many protocluster candidates are found by chance for randomly distributed sources, and find that the effective number of protocluster candidates at z = 5.7 (6.6) is six (five). By comparing with the cosmological Ly alpha radiative transfer (RT) model reproducing the LAEs with reionization effects, we find that more than half of these protocluster candidates are progenitors of present-day clusters with mass of greater than or similar to 10(14)M(circle dot). We then investigate the correlation between the LAE overdensity delta and the Ly alpha rest-frame equivalent width EWLy alpha rest, because the cosmological Ly alpha RT model suggests that the slope of the EWLy alpha rest-delta relation steepens toward the epoch of cosmic reionization (EoR), due to the existence of ionized bubbles around galaxy overdensities easing the escape of Ly alpha emission from the partly neutral intergalactic medium. The available HSC data suggest that the slope of the EWLy alpha rest-delta correlation does not evolve from the post-reionization epoch, z = 5.7, to the EoR, z = 6.6, beyond the moderately large statistical errors. There is a possibility that we could detect the evolution of the EWLy alpha rest-delta relation from z = 5.7 to 7.3 using the upcoming HSC observations that will provide large samples of LAEs at z = 6.6-7.3.
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SponsorsFIRST program from the Japanese Cabinet Office; Ministry of Education, Culture, Sports, Science and Technology (MEXT); Japan Society for the Promotion of Science (JSPS); Japan Science and Technology Agency (JST); Toray Science Foundation; NAOJ; Kavli IPMU; KEK; ASIAA; Princeton University; National Aeronautics and Space Administration [NNX08AR22G]; National Science Foundation [AST-1238877]; Ehime University; KAKENHI through the Japan Society for the Promotion of Science [23244025, 15H02064]; World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan; Hayakawa Satio Fund - Astronomical Society of Japan