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Title: DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA

Abstract

Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα 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 Hα 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-linemore » 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.« less

Authors:
;  [1];  [2];  [3];  [4];  [5]
  1. Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807 (United States)
  2. Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)
  3. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)
  4. Department of Physics and Astronomy, University of California, Irvine, CA 92697-4575 (United States)
  5. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
Publication Date:
OSTI Identifier:
22521828
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 814; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; COMPARATIVE EVALUATIONS; DENSITY; EMISSION SPECTRA; EXCITATION; GALAXIES; GALAXY NUCLEI; LUMINOSITY; POTENTIALS; QUASARS; RESOLUTION; SENSITIVITY; SPACE; STARS; TELESCOPES

Citation Formats

Constantin, Anca, Castillo, Christopher A., Shields, Joseph C., Ho, Luis C., Barth, Aaron J., and Filippenko, Alexei V. DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA. United States: N. p., 2015. Web. doi:10.1088/0004-637X/814/2/149.
Constantin, Anca, Castillo, Christopher A., Shields, Joseph C., Ho, Luis C., Barth, Aaron J., & Filippenko, Alexei V. DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA. United States. https://doi.org/10.1088/0004-637X/814/2/149
Constantin, Anca, Castillo, Christopher A., Shields, Joseph C., Ho, Luis C., Barth, Aaron J., and Filippenko, Alexei V. 2015. "DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA". United States. https://doi.org/10.1088/0004-637X/814/2/149.
@article{osti_22521828,
title = {DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA},
author = {Constantin, Anca and Castillo, Christopher A. and Shields, Joseph C. and Ho, Luis C. and Barth, Aaron J. and Filippenko, Alexei V.},
abstractNote = {Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα 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 Hα 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.},
doi = {10.1088/0004-637X/814/2/149},
url = {https://www.osti.gov/biblio/22521828}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 814,
place = {United States},
year = {Tue Dec 01 00:00:00 EST 2015},
month = {Tue Dec 01 00:00:00 EST 2015}
}