Deep-imaging observations of a candidate of an absorbed QSO at z = 0.653, AX J131831+3341

Masayuki Akiyama, Kouji Ohta, Naoyuki Tamura, Mamoru Doi, Masahiko Kimura, Yutaka Komiyama, Satoshi Miyazaki, Fumiaki Nakata, Sadanori Okamura, Maki Sekiguchi, Kazuhiro Shimasaku, Masafumi Yagi, Masaru Hamabe, Michitoshi Yoshida, Tadahumi Takata

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2 Citations (Scopus)


The results of deep-imaging observations of a candidate of an absorbed QSO at z = 0.653, AX J131831+3341, are presented. AX J131831+3341 was found during the course of optical follow-up observations of the ASCA Large Sky Survey, and has an X-ray luminosity of 1045 erg s-1 (2-10 keV), which corresponds to those of QSOs. Its optical spectrum shows no significant broad Hβ emission line, suggesting that the object is an absorbed QSO. Deep R and V band images reveal the presence of a point-like nucleus and an asymmetric extended component. The nuclear component has a blue color, and the optical magnitude is much fainter than that expected from the observed X-ray flux for typical type-1 AGNs. These photometric properties and the presence of broad Mg II 2800 Å emission can be explained simultaneously if the observed nuclear light is dominated by scattered nuclear light, though there is a possibility that the nuclear component is a slightly absorbed nucleus if its intrinsic X-ray to optical flux ratio is the largest among X-ray selected AGNs. The size of the extended component, which is thought to be the host galaxy of the QSO, is larger than those of normal disk galaxies at z = 0-0.75, and the absolute magnitude is similar to those of the brightest host galaxies of QSOs at redshifts smaller than 0.5. The V - R and R - I colors of the component are consistent with a 1 Gyr-old stellar population model without absorption.

Original languageEnglish
Pages (from-to)577-584
Number of pages8
JournalPublications of the Astronomical Society of Japan
Issue number4
Publication statusPublished - 2000
Externally publishedYes


  • Galaxies: Active
  • Galaxies: Individual (AX J131831+3341)
  • Galaxies: Photometry
  • Quasars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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