An Observational Link between AGN Eddington Ratio and [N ii]λ6583/Hα at 0.6 < z < 1.7

Kyuseok Oh, Yoshihiro Ueda, Masayuki Akiyama, Hyewon Suh, Michael J. Koss, Daichi Kashino, Günther Hasinger

Research output: Contribution to journalArticlepeer-review

Abstract

We present an observed relationship between the Eddington ratio (λ Edd) and the optical narrow-emission-line ratio ([N ii]λ6583/Hα) of X-ray-selected broad-line active galactic nuclei (AGNs) at 0.6 < z < 1.7. We use 27 near-infrared spectra from the Fiber Multi-Object Spectrograph along with 26 sources from the literature. We show that the λ Edd and [N ii]λ6583/Hα ratio at 0.6 < z < 1.7 exhibits a similar anti-correlation distribution of λ Edd-[N ii]λ6583/Hα, as has been found for local (), ultra-hard, X-ray-selected AGNs. The observed distribution implies that there is a consistent relationship from local to z ∼ 1.7, which corresponds from the present time to 4 Gyr old. Further study of high-redshift, low-Eddington-ratio AGNs (log λ Edd < -2) is necessary to determine fully whether the λ Edd-[N ii]λ6583/Hα anti-correlation still holds in high-redshift AGNs at low Eddington ratios.

Original languageEnglish
Article number112
JournalAstrophysical Journal
Volume880
Issue number2
DOIs
Publication statusPublished - 2019 Aug 1

Keywords

  • galaxies: Seyfert
  • galaxies: active
  • galaxies: nuclei
  • quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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