Subaru high-z exploration of low-luminosity quasars (shellqs). xiv. a candidate type ii quasar at z=6.1292

Masafusa Onoue, Yoshiki Matsuoka, Nobunari Kashikawa, Michael A. Strauss, Kazushi Iwasawa, Takuma Izumi, Tohru Nagao, Naoko Asami, Seiji Fujimoto, Yuichi Harikane, Takuya Hashimoto, Masatoshi Imanishi, Chien Hsiu Lee, Takatoshi Shibuya, Yoshiki Toba

Research output: Contribution to journalArticlepeer-review

Abstract

We present deep Keck/MOSFIRE near-infrared spectroscopy of a strong Lyα emitting source at z = 6.1292, HSC J142331.71-001809.1, which was discovered by the SHELLQS program from imaging data of the Subaru Hyper Suprime-Cam (HSC) survey. This source is one of five objects that show narrow (FWHM < 500 km s-1) and prominent (LLyα > 1044 erg s-1) Lyα emission lines at absolute 1450 Å continuum magnitudes of M1450∼-22 mag. Its rest-frame Lyα equivalent width (EW) is 370 ± 30 Å. In the 2 hr Keck/MOSFIRE spectrum in Y band, the high-ionization C IV λλ1548,1550 doublet emission line was clearly detected with = - FWHM 120+20 20 km s-1 and a total rest-frame EW of - 37+5 6 Å. We also report the detection of weak continuum emission, and the tentative detection of O III]λλ1661,1666 in the 4 hr J-band spectrum. Judging from the UV magnitude, line widths, luminosities, and EWs of Lyα and C IV, we suggest that this source is a reionization-era analog of classical type-II AGNs, although there is a possibility that it represents a new population of AGN/galaxy composite objects in the early universe. We compare the properties of J1423-0018 to intermediate-redshift type-II AGNs and C IV emitters seen in z = 6-7 galaxy samples. Further observations of other metal emission lines in the rest-frame UV or optical, along with X-ray follow-up observations of the z = 6-7 narrow-line quasars, are needed for more robust diagnostics and to determine their nature.

Original languageEnglish (US)
Article number61
JournalAstrophysical Journal
Volume919
Issue number1
DOIs
StatePublished - Sep 20 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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