A Search for “Dwarf” Seyfert Nuclei. VI. Properties of Emission-Line Nuclei in Nearby Galaxies

By Luis C. Ho, A. Filippenko, W. Sargent. 2002

143 citations recorded by the source corpus.

We use the database from Paper III to quantify the global and nuclear properties of emission-line nuclei in the Palomar spectroscopic survey of nearby galaxies. We show that the host galaxies of Seyferts, LINERs, and transition objects share remarkably similar large-scale properties and local environments. The distinguishing traits emerge on nuclear scales. Compared with LINERs, Seyfert nuclei are an order of magnitude more luminous and exhibit higher electron densities and internal extinction. We suggest that Seyfert galaxies possess characteristically more gas-rich circumnuclear regions and hence a more abundant fuel reservoir and plausibly higher accretion rates. The differences between the ionization states of the narrow emission-line regions of Seyferts and LINERs can be partly explained by the differences in their nebular properties. Transition-type objects are consistent with being composite (LINER/H II) systems. With very few exceptions, the stellar population within the central few hundred parsecs of the host galaxies is uniformly old, a finding that presents a serious challenge to starburst or post-starburst models for these objects. Seyferts and LINERs have virtually indistinguishable velocity fields as inferred from their line widths and line asymmetries. Transition nuclei tend to have narrower lines and more ambiguous evidence for line asymmetries. All three classes of objects obey a strong correlation between line width and line luminosity. We argue that the angular momentum content of circumnuclear gas may be an important factor in determining whether a nucleus becomes active. Finally, we discuss some possible complications for the unification model of Seyfert galaxies posed by our observations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e24d5903eea3068a6122b04fb66e936810c3ec94

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Citations in the corpus

What drives the growth of black holes (2011, background): “…AGN– star-forming galaxies, optically obscured AGNs, lowluminosity AGNs, and early type galaxies without AGN activity (e.g., Binette et al., 1994; Ho et al., 2001, 2003; Eracleous et al., 2002; Satyapal et al., 2004; Kewley et al., 2006; Shields et al., 2007; González-Martı́n et al., 2009;…”
THE FUNDAMENTAL PLANE OF ACCRETION ONTO BLACK HOLES WITH DYNAMICAL MASSES (2009, methodology): “…Seyferts and LINERs is judged from the line ratios with the usual diagnostic and division set so that Seyferts have [OIII]λ5007/Hβ > 3.0 (Veilleux & Osterbrock 1987) as a measurement of the level of nuclear ionization, though there is no obvious transition between the two classes (Ho et al. 2003).”
The host galaxies of active galactic nuclei (2003, unknown): “The stellar populations in the nuclei of weak AGN are predominantly old (e.g. Ho et al. 2003), while a young stellar population is clearly present in about half of powerful type 2 Seyfert nuclei (e.g. Cid Fernandes et al. 2001; Joguet et al. 2001).”
The host galaxies and classification of active galactic nuclei (2006, result): “Ho et al. (2003) found a similar result for the central few hundred parsecs of Seyferts and LINERs and they suggest that Seyfert galaxies contain nuclear regions that are more gas-rich (and dusty) than LINER galaxies.”
Evolution of broad-line emission from active galactic nuclei (2013, background): “For example, the upper limits to the broad Hα luminosity for the majority of the type 2 sources in the Palomar survey (Ho et al. 1997, 2003) are not inconsistent with the level of detected X-ray emission (Ho 2009).”
Radio sources in low-luminosity active galactic nuclei IV. Radio luminosity function, importance of jet power, and radio properties of the complete Palomar sample (2005, methodology): “The nuclear environments of low-luminosity Palomar Seyferts are richer in gas than those of Palomar LINERs (Ho et al. 2003a), as inferred from higher electron densities (ne) and higher internal extinction in the former class.”
Alternative diagnostic diagrams and the 'forgotten' population of weak line galaxies in the SDSS (2009, background): “Since the narrow-line region of Seyferts is generally denser than that of LINERs (Ho et al. 2003), this could be yet another cause for the marked split seen in Fig.”
The Low End of the Supermassive Black Hole Mass Function: Constraining the Mass of a Nuclear Black Hole in NGC 205 via Stellar Kinematics (2005, background): “The galaxy shows no sign of nuclear activity (Ho et al. 2003; Fabbiano et al. 1992; Condon et al. 1998).”
Molecular gas in NUclei of GAlaxies (NUGA) - IV. Gravitational torques and AGN feeding (2005, unknown): “The different values of AGN duty-cycles discussed in the literature range from 107 to 108 yr (Ho et al. 2003; Martini 2004; Wada 2004; Merloni 2004).”
RADIATIVELY INEFFICIENT ACCRETION IN NEARBY GALAXIES (2009, methodology): “Since the various classes of emission-line nuclei in the Palomar survey are hosted by slightly different Hubble types (Ho et al. 2003a), it would be of interest to examine the trends inLbol and Lbol/LEdd after factoring out the dependence on Hubble type.”