Probing the physics of narrow-line regions of Seyfert galaxies I: The case of NGC 5427

Abstract

We have used the Wide Field Spectrograph (WiFeS) on the ANU 2.3m telescope at Siding Spring to observe the nearby, nearly face-on, Seyfert 2 galaxy, NGC 5427. We have obtained integral field spectroscopy of both the nuclear regions and the HII regions in the spiral arms. We have constrained the chemical abundance in the interstellar medium of the extended narrow line region (ENLR) by measuring the abundance gradient in the circum-nuclear \ion{H}{ii} regions to determine the nuclear chemical abundances, and to use these to in turn determine the EUV spectral energy distribution for comparison with theoretical models. We find a very high nuclear abundance, $\sim 3.0$ times solar, with clear evidence of a nuclear enhancement of N and He, possibly caused by massive star formation in the extended ($\sim 100$pc) central disk structure. The circum-nuclear narrow-line region spectrum is fit by a radiation pressure dominated photoionisation model model with an input EUV spectrum from a Black Hole with mass $5\times 10^7{M}_{\odot }$ radiating at $\sim 0.1$ of its Eddington luminosity. The bolometric luminosity is closely constrained to be $\log L_{\mathrm{b}ol.}=44.3\pm 0.1$ erg s${}^{-1}$. The EUV spectrum characterised by a soft accretion disk and a harder component extending to above 15keV. The ENLR region is extended in the NW-SE direction. The line ratio variation in circum-nuclear spaxels can be understood as the result of mixing \ion{H}{ii} regions with an ENLR having a radius-invariant spectrum.

Accepted for publication in Astronomy and Astrophysics, 14 pages, 13 figures

References in corpus (8)

• The Host Galaxies and Classification of Active Galactic Nuclei
• The Wide Field Spectrograph (WiFeS): Performance and Data Reduction
• Resolving the electron temperature discrepancies in HII Regions and Planetary Nebulae: kappa-distributed electrons
• Star formation in accretion discs : from the Galactic Center to Active Galactic Nuclei
• Theoretical calculations of the HI, HeI and HeII free-bound continuou emission spectra
• Evolution of chemical abundances in Seyfert galaxies
• Chandra Observations of Candidate "True" Seyfert 2 Nuclei
• Extended narrow-line emission in the bright Seyfert 1.5 galaxy HE 2211-3903

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