Modelling narrow-line regions of active galaxies in the Sloan Digital Sky Survey - I.Sample selection and physical conditions

Abstract

We systematically determine the electron density and electron temperature of active galaxies and star-forming galaxies using spectroscopy from the SDSS DR7, while mainly focusing on the NLRs. Density and temperature are determined through the I[S II] 6716/6731 and I[O III] 5007/4363 ratios, respectively, in our [O III] 4363 emission sample of 15 019 galaxies. We find two sequences and the typical range of density in the NLRs of AGNs is 100-1000 /cm3. The temperatures in the NLRs range from 10 000 to 20 000 K for Seyferts, and the ranges were even higher and wider for LINERs and composites. We also propose that Y_LINER ~ Y_Seyfert > Y_composite > Y_star-forming, where Y is the characteristic present-day star-formation time-scale. While in the AGN case, we find several strong lines of evidence suggest that some supplementary energy source(s) should be responsible for high ionization potential.

17 pages, 12 figures, 10 tables; the first paragraph in Section 7.2 cited from arXiv:astro-ph/0607311; MNRAS in press

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• New metallicity calibration for Seyfert 2 galaxies based on the N2O2 index
• Semi-empirical metallicity calibrations based on ultraviolet emission lines of type-2 AGNs
• Chemical abundances of Seyfert 2 AGNs IV. Composite models calculated by photoionization + shocks
• An X-ray/SDSS sample (II): outflowing gas plasma properties
• Gas phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA: evidence of metal poor accretion
• Constraints on the densities and temperature of Seyfert 2 NLR
• Do gas clouds in narrow-line regions of Seyfert galaxies come from their nuclei?
• Electron Energy Distributions in the Extended Gas Nebulae associated with High-z AGN: Maxwell-Boltzmann vs. kappa distributions
• Kinematic study of the parsec-scale jet of the quasar PKS 1741--03