Astrophys. J., 593, 115-126 (2003/August-2)
Emission-line diagnostics of the central engines of weak-line radio galaxies.
LEWIS K.T., ERACLEOUS M. and SAMBRUNA R.M.
Abstract (from CDS):
A handful of well-studied weak-line radio galaxies (WLRGs) have been traditionally classified as low-ionization nuclear emission-line regions (LINERs), suggesting that these two groups of active galactic nuclei (AGNs) might be related. In this paper, we present new optical emission-line measurements for 20 WLRGs, which we supplement with measurements for an additional four from the literature. Classifying these objects by their emission-line ratios, we find that 50% of the objects are robustly classified as LINERs, while an additional 25% are likely to be LINERs. Photoionization calculations show that the spectral energy distribution of the well-studied WLRG 3C 270 (NGC 4261) is able to produce the observed emission-line ratios, but only if the UV emission seen by the narrow emission line gas is significantly higher than that observed, implying AV=2.5-4.2 mag along our line of sight to the nucleus. From the photoionization calculations, we find that the emission-line gas must have an ionization parameter between 10–3.5 and 10–4.0 and a wide range in hydrogen density (102-106 cm–3) to reproduce the measured emission-line ratios, similar to the properties inferred for the emission-line gas in LINERs. Thus, we find that properties of the emission-line gas as well as the underlying excitation mechanism are indeed similar in LINERs and WLRGs. By extension, the central engines of accretion-powered LINERs and WLRGs, which do host an accreting black hole, may be qualitatively similar.
Galaxies: Active - Galaxies: Nuclei
Table 1 : 0427-53 = IC 2082 ? (IC 2080 does not exist)
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