Journal article
Tracing quasar narrow-line regions across redshift: a library of high-S/N optical spectra
Monthly notices of the Royal Astronomical Society, v 448(4), pp 3354-3362
21 Apr 2015
Abstract
In a single optical spectrum, the quasar narrow-line region (NLR) reveals low-density, photoionized gas in the host galaxy interstellar medium (ISM), while the immediate vicinity of the central engine generates the accretion disc continuum and broad emission lines. To isolate these two components, we construct a library of high-S/N optical composite spectra created from the Sloan Digital Sky Survey Data Release 7. We divide the sample into bins of continuum luminosity and H beta full width at half-maximum that are used to construct median composites at different redshift steps up to 0.75. We measure the luminosities of the narrow-emission lines [Ne V] lambda 3427, [Ne III].3870, [O III].5007, and [O II] lambda 3728 with ionization potentials (IPs) of 97, 40, 35, and 13.6 eV, respectively. The high IP lines' luminosities show no evidence of increase with redshift consistent with no evolution in the AGN spectral energy distribution or the host galaxy ISM illuminated by the continuum. In contrast, we find that the [OII] line becomes stronger at higher redshifts, and we interpret this as a consequence of enhanced star formation contributing to the [O II] emission in host galaxies at higher redshifts. The SFRs estimated from the [OII] luminosities show a flatter increase with z than non-AGN galaxies given our assumed AGN contribution to the [O II] luminosity. Finally, we confirm an inverse correlation between the strength of the Fe II.4570 complex and both the [O III] equivalent width (though not the luminosity) and the width of the H beta line as known from the eigenvector 1 correlations.
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Details
- Title
- Tracing quasar narrow-line regions across redshift: a library of high-S/N optical spectra
- Creators
- A. Tammour - Western UniversityS. C. Gallagher - Western UniversityGordon Richards - Drexel University
- Publication Details
- Monthly notices of the Royal Astronomical Society, v 448(4), pp 3354-3362
- Publisher
- Oxford Univ Press
- Number of pages
- 9
- Grant note
- Max Planck Society; Foundation CELLEX National Science Foundation; National Science Foundation (NSF) Schlumberger Foundation - Faculty for the Future Program; Schlumberger Natural Science and Engineering Research Council of Canada; Natural Sciences and Engineering Research Council of Canada (NSERC) National Aeronautics and Space Administration; National Aeronautics & Space Administration (NASA) Ontario Early Researcher Award Program; Ministry of Research and Innovation, Ontario Alfred P. Sloan Foundation Higher Education Funding Council for England; UK Research & Innovation (UKRI); Higher Education Funding Council for England (HEFCE) Japanese Monbukagakusho; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) US Department of Energy; United States Department of Energy (DOE)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000351529500029
- Scopus ID
- 2-s2.0-84942155844
- Other Identifier
- 991019168585104721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Astronomy & Astrophysics