NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-20 T01:58:01 PDT
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For refcode 2015ApJ...814..149C:
Retrieve 90 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2015ApJ...814..149C Dissecting the Power Sources of Low-Luminosity Emission-Line Galaxy Nuclei via Comparison of HST-STIS and Ground-Based Spectra Constantin, Anca; Shields, Joseph C.; Ho, Luis C.; Barth, Aaron J.; Filippenko, Alexei V.; Castillo, Christopher A. Abstract. Using a sample of ~100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Halpha and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which transition objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at <~10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in the line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The transition objects show a threefold increase in the incidence of broad Halpha emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z ~ 0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Key words: galaxies: active, galaxies: nuclei, quasars: emission lines
Retrieve 90 NED objects in this reference.
Please click here for ADS abstract

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