期刊
ASTROPHYSICAL JOURNAL
卷 747, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/0004-637X/747/1/61
关键词
galaxies: active; galaxies: elliptical and lenticular, cD; galaxies: ISM; ISM: kinematics and dynamics; stars: AGB and post-AGB
资金
- National Science Foundation (NSF) [AST-0908354]
- National Aeronautics and Space Administration (NASA) [08-ADP08-0019m, 08-ADP08-0072]
- Alfred P. Sloan Foundation
- U.S. Department of Energy
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- University of Chicago
- Fermilab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max-Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- University of Pittsburgh
- Princeton University
- United States Naval Observatory
- University of Washington
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0908354] Funding Source: National Science Foundation
Passive red galaxies frequently contain warm ionized gas and have spectra similar to low-ionization nuclear emission-line regions (LINERs). Here we investigate the nature of the ionizing sources powering this emission, by comparing nuclear spectroscopy from the Palomar survey with larger aperture data from the Sloan Digital Sky Survey. We find the line emission in the majority of passive red galaxies is spatially extended; the H alpha surface brightness profile depends on radius r as r(-1.28). We detect strong line ratio gradients with radius in [N II]/H alpha, [S II]/H alpha, and [O III]/[S II], requiring the ionization parameter to increase outward. Combined with a realistic gas density profile, this outward increasing ionization parameter convincingly rules out active galactic nuclei (AGNs) as the dominant ionizing source and strongly favors distributed ionizing sources. Sources that follow the stellar density profile can additionally reproduce the observed luminosity dependence of the line ratio gradient. Post-asymptotic giant branch stars provide a natural ionization source candidate, though they have an ionization parameter deficit. Velocity width differences among different emission lines disfavor shocks as the dominant ionization mechanism, and suggest that the interstellar medium in these galaxies contains multiple components. We conclude that the line emission in most LINER-like galaxies found in large-aperture (> 100 pc) spectroscopy is not primarily powered by AGN activity and thus does not trace the AGN bolometric luminosity. However, they can be used to trace warm gas in these red galaxies.
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