研究成果・発表論文

SILVERRUSH. VI. A simulation of Ly\ensuremathα emitters in the reionization epoch and a comparison with Subaru Hyper Suprime-Cam survey early data

Inoue, Akio K.,   Hasegawa, Kenji,   Ishiyama, Tomoaki,   Yajima, Hidenobu,   Shimizu, Ikkoh,   Umemura, Masayuki,   Konno, Akira,   Harikane, Yuichi,   Shibuya, Takatoshi,   Ouchi, Masami,   Shimasaku, Kazuhiro,   Ono, Yoshiaki,   Kusakabe, Haruka,   Higuchi, Ryo,   & Lee, Chien-Hsiu


要旨
The survey of Lyman \ensuremathα emitters (LAEs) with the Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al. 2018, PASJ, 70, S13), is producing massive data of LAEs at z \ensuremath\gtrsim 6. Here we present LAE simulations to compare the SILVERRUSH data. In 162$^3$ comoving Mpc$^3$ boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined 2$^3$ models depending on the presence or absence of dispersion of halo Ly\ensuremathα emissivity, dispersion of the halo Ly\ensuremathα optical depth, \ensuremathτ$_\ensuremathα$, and halo mass dependence of \ensuremathτ$_\ensuremathα$. The unique free parameter in our model, a pivot value of \ensuremathτ$_\ensuremathα$, is calibrated so as to reproduce the z = 5.7 Ly\ensuremathα luminosity function (LF) of SILVERRUSH. We compare our model predictions with Ly\ensuremathα LFs at z = 6.6 and 7.3, LAE angular auto-correlation functions (ACFs) at z = 5.7 and 6.6, and LAE fractions in Lyman break galaxies at 5 < z < 7. The Ly\ensuremathα LFs and ACFs are reproduced by multiple models, but the LAE fraction turns out to be the most critical test. The dispersion of \ensuremathτ$_\ensuremathα$ and the halo mass dependence of \ensuremathτ$_\ensuremathα$ are essential to explain all observations reasonably. Therefore, a simple model of one-to-one correspondence between halo mass and Ly\ensuremathα luminosity with a constant Ly\ensuremathα escape fraction has been ruled out. Based on our best model, we present a formula to estimate the intergalactic neutral hydrogen fraction, x_\H I\, from the observed Ly\ensuremathα luminosity density at z \ensuremath\gtrsim 6. We finally obtain x_\H I\=0.5_\-0.3\\̂+0.1\ as a volume-average at z = 7.3.






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