Subaru medium-resolution spectra of a QSO at z=6.62: Three reionization tests

Investigating the Gunn-Peterson trough of high redshift quasars (QSOs) is a powerful way to reveal the cosmic reionization. As one of such attempts, we perform a series of analyses to examine the absorption lines observed with one of the highest redshift QSOs, PSO J006.1240+39.2219, which we previously discovered at z = 6.62. Using the Subaru telescope, we obtained medium-resolution spectrum with a total exposure time of 7.5 hours. We calculate the Ly$\alpha$ transmission in different redshift bins to determine the near zone radius and the optical depth at 5.6$$5.8). All three analyses based on this QSO show increasingly neutral hydrogen towards higher redshifts, adding precious measurements up to z$\sim$6.5.
Comment: 11 pages, 10 figures, 5 tables, Accepted for Publication in ApJ