An Optically Faint Quasar Survey at z ∼ 5 in the CFHTLS Wide Field: Estimates of the Black Hole Masses and Eddington Ratios

H. Ikeda, T. Nagao, K. Matsuoka, N. Kawakatu, M. Kajisawa, M. Akiyama, T. Miyaji, T. Morokuma

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5 Citations (Scopus)

Abstract

We present the result of our spectroscopic follow-up observation for faint quasar candidates at z ∼ 5 in part of the Canada-France-Hawaii Telescope Legacy Survey wide field. We select nine photometric candidates and identify three z ∼ 5 faint quasars, one z ∼ 4 faint quasar, and a late-type star. Since two faint quasar spectra show the C iv emission line without suffering from a heavy atmospheric absorption, we estimate their black hole masses (MBH) and Eddington ratios (L/LEdd). The inferred logMBH are 9.04 ± 0.14 and 8.53 ± 0.20, respectively. In addition, the inferred are -1.00 ± 0.15 and -0.42 ± 0.22, respectively. If we adopt that L/LEdd = constant or |∞ (1 + Z)2, the seed black hole masses (Msced) of our z ∼ 5 faint quasars are expected to be > 105 MOin most cases. We also compare the observational results with a mass accretion model, where angular momentum is lost due to supernova explosions. Accordingly, of the z ∼ 5 faint quasars in our sample can be explained even if Msced is ∼ 103 Mo. Since z ∼ 6 luminous qusars and our z ∼ 5 faint quasars are not on the same evolutionary track, z ∼ 6 luminous quasars and our z ∼ 5 quasars are not the same populations but different populations, due to the difference of a period of the mass supply from host galaxies. Furthermore, we confirm that one can explain of z ∼ 6 luminous quasars and our z ∼ 5 faint quasars even if their seed black holes are formed at z ∼ 7.

Original languageEnglish
Article number57
JournalAstrophysical Journal
Volume846
Issue number1
DOIs
Publication statusPublished - 2017 Sep 1

Keywords

  • cosmology: observations
  • quasars: supermassive black holes-surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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