X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

Yuichi Terashima, Makoto Suganuma, Masayuki Akiyama, Jenny E. Greene, Toshihiro Kawaguchi, Kazushi Iwasawa, Tohru Nagao, Hirofumi Noda, Yoshiki Toba, Yoshihiro Ueda, Takuji Yamashita

Research output: Contribution to journalArticle

Abstract

We construct a sample of X-ray-bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. Fifty-three Xray sources satisfying i-band magnitude fainter than 23.5 mag and X-ray counts with the EPIC-PN detector larger than 70 are selected from 9.1 deg2, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. Forty-four objects with an X-ray to i-band flux ratio FX/Fi > 10 are classified as extreme X-ray-to-optical flux sources. Spectral energy distributions of 48 among 53 are represented by templates of type 2 AGNs or star-forming galaxies and show the optical signature of stellar emission from host galaxies in the source rest frame. Infrared/optical SEDs indicate a significant contribution of emission from dust to the infrared fluxes, and that the central AGN is dust obscured. The photometric redshifts determined from the SEDs are in the range of 0.6-2.5. The X-ray spectra are fitted by an absorbed power-law model, and the intrinsic absorption column densities are modest (best-fit logNH = 20.5-23.5 cm-2 in most cases). The absorptioncorrected X-ray luminosities are in the range of 6 × 1042-2 × 1045 erg s-1. Twenty objects are classified as type 2 quasars based on X-ray luminsosity and NH. The optical faintness is explained by a combination of redshifts (mostly z > 1.0), strong dust extinction, and in part a large ratio of dust/gas.

Original languageEnglish (US)
Article numberS36
JournalPublications of the Astronomical Society of Japan
Volume70
Issue numberSpecial Issue 1
DOIs
StatePublished - Jan 1 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Active-galaxies
  • Galaxies
  • Galaxies
  • Supermassive black hole-X-rays

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    Terashima, Y., Suganuma, M., Akiyama, M., Greene, J. E., Kawaguchi, T., Iwasawa, K., Nagao, T., Noda, H., Toba, Y., Ueda, Y., & Yamashita, T. (2018). X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey. Publications of the Astronomical Society of Japan, 70(Special Issue 1), [S36]. https://doi.org/10.1093/pasj/psx109