Do gas clouds in narrow-line regions of Seyfert galaxies come from their nuclei?

Abstract

The narrow-line region (NLR) consists of gas clouds ionized by the strong radiation from the active galactic nucleus (AGN), distributed in the spatial scale of AGN host galaxies. The strong emission lines from the NLR are useful to diagnose physical and chemical properties of the interstellar medium in AGN host galaxies. However, the origin of the NLR is unclear; the gas clouds in NLRs may be originally in the host and photoionized by the AGN radiation, or they may be transferred from the nucleus with AGN-driven outflows. For studying the origin of the NLR, we systematically investigate the gas density and velocity dispersion of NLR gas clouds using a large spectroscopic data set taken from the Sloan Digital Sky Survey. The [S II] emission-line flux ratio and [O III] velocity width of 9,571 type-2 Seyfert galaxies and 110,041 star-forming galaxies suggest that the gas density and velocity dispersion of NLR clouds in Seyfert galaxies (ne ~ 194 cm-3 and sigma([O III]) ~ 147 km s-1) are systematically larger than those of clouds in H II regions of star-forming galaxies (ne ~ 29 cm-3 and sigma([O III]) ~ 58 km s-1). Interestingly, the electron density and velocity dispersion of NLR gas clouds are larger for Seyfert galaxies with a higher [O III]/Hbeta flux ratio, i.e., with a more active AGN. We also investigate the spatially-resolved kinematics of ionized gas clouds using the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey data for 90 Seyfert galaxies and 801 star-forming galaxies. We find that the velocity dispersion of NLR gas clouds in Seyfert galaxies is larger than that in star-forming galaxies at a fixed stellar mass, at both central and off-central regions. These results suggest that gas clouds in NLRs come from the nucleus, probably through AGN outflows.

15 pages, 13 figures, 1 table. Accepted for publication in PASJ

References in corpus (16)

• The Host Galaxies and Classification of Active Galactic Nuclei
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• Radio-Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications
• The Data Reduction Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey
• Star formation in a galactic outflow
• Kinematics of the Narrow-Line Region in the Seyfert 2 Galaxy NGC 1068: Dynamical Effects of the Radio Jet
• SDSS IV MaNGA - The spatially resolved transition from star formation to quiescence
• The triggering probability of radio-loud AGN: A comparison of high and low excitation radio galaxies in hosts of different colors
• Properties of ionized outflows in MaNGA DR2 galaxies
• The Interplay Between Star Formation and Black Hole Accretion in Nearby Active Galaxies
• Integral Field Spectroscopy of the Extended Emission-Line Region of 4C 37.43
• Modelling narrow-line regions of active galaxies in the Sloan Digital Sky Survey - I.Sample selection and physical conditions
• The first 62 AGN observed with SDSS-IV MaNGA -- III: stellar and gas kinematics
• Near-infrared spectroscopy of nearby Seyfert galaxies: Is there evidence for the shock excitation in narrow-line regions?
• Multi-wavelength observations of the triple-peaked AGN Mrk 622

Cited by in corpus (3)

• Optical IFU Observations of GOALS Sample with KOOLS-IFU on Seimei Telescope: Initial results of 9 U/LIRGs at $z<$ 0.04
• Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 quasar
• Forgotten treasures in the HST/FOC UV imaging polarimetric archives of active galactic nuclei. II. Mrk 463E