Multiline Assessment of Narrow-line Regions in z similar to 3 Radio Galaxies
Journal article, 2022

In this paper, we use high-quality rest-UV spectra of three radio galaxies at z similar to 3 observed with the FORS2 camera on the Very Large Telescope to measure the flux of several emission lines, including relatively faint ones, such as N iv]lambda 1486, O iii]lambda 1663, and [Ne iv]lambda 2424. Additionally, we collect fluxes of faint rest-UV emission lines in 12 z similar to 3 radio galaxies from the literature. Previously, physical and chemical properties of narrow-line regions (NLRs) in high-z active galactic nuclei (AGNs) have been investigated mostly by using only strong rest-UV emission lines (e.g., N v lambda 1240, C iv lambda 1549, He ii lambda 1640, and C iii]lambda 1909). Such strong-line diagnostics are based on various assumptions due to the limitation in the number of available emission-line constraints. In this work, both physical and chemical properties of NLR clouds in each object are estimated by fitting detailed photoionization models to the measured emission-line fluxes. We confirm that the metallicity of NLRs in AGNs at z similar to 3 is solar or supersolar, without assumptions about the gas density and ionization parameter thanks to the constraints from the faint emission lines. This result suggests that high-z radio galaxies are already chemically mature at z similar to 3.

Author

Koki Terao

Tohoku University

Tohru Nagao

Ehime University

Kyoko Onishi

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Kenta Matsuoka

Utena Meishu Company Ltd

Masayuki Akiyama

Tohoku University

Yoshiki Matsuoka

Ehime University

Takuji Yamashita

Ehime University

National Astronomical Observatory of Japan

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 929 1 51

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Environmental Sciences

DOI

10.3847/1538-4357/ac5b71

More information

Latest update

4/28/2022