Exploring Changes in Quasar Spectral Energy Distributions across C iv Parameter Space
Publication Date
2022Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
American Astronomical Society
Volume
931
Issue
2
Language
en
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Rivera, A., Richards, G., Gallagher, S., McCaffrey, T., Rankine, A., Hewett, P., & Shemmer, O. (2022). Exploring Changes in Quasar Spectral Energy Distributions across C iv Parameter Space. Astrophysical Journal, 931 (2) https://doi.org/10.3847/1538-4357/ac6a5d
Abstract
<jats:title>Abstract</jats:title>
<jats:p>We examine the UV/X-ray properties of 1378 quasars in order to link empirical correlations to theoretical models of the physical mechanisms dominating quasars as a function of mass and accretion rate. The clarity of these correlations is improved when (1) using C <jats:sc>iv</jats:sc> broad emission line equivalent width (EQW) and blueshift (relative to systemic) values calculated from high signal-to-noise ratio reconstructions of optical/UV spectra and (2) removing quasars expected to be absorbed based on their UV/X-ray spectral slopes. In addition to using the traditional C <jats:sc>iv</jats:sc> parameter space measures of C <jats:sc>iv</jats:sc> EQW and blueshift, we define a “C <jats:sc>iv</jats:sc> ∥ distance” along a best-fit polynomial curve that incorporates information from both C <jats:sc>iv</jats:sc> parameters. We find that the C <jats:sc>iv</jats:sc> ∥ distance is linearly correlated with both the optical-to-X-ray slope, <jats:italic>α</jats:italic>
<jats:sub>ox</jats:sub>, and broad-line He <jats:sc>ii</jats:sc> EQW, which are known spectral energy distribution indicators, but does not require X-ray or high spectral resolution UV observations to compute. The C <jats:sc>iv</jats:sc> ∥ distance may be a better indicator of the mass-weighted accretion rate, parameterized by <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic>
<jats:sub>Edd</jats:sub>, than the C <jats:sc>iv</jats:sc> EQW or blueshift alone, as those relationships are known to break down at the extrema. Conversely, there is only a weak correlation with the X-ray energy index (Γ), an alternate <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic>
<jats:sub>Edd</jats:sub> indicator. We find no X-ray or optical trends in the direction perpendicular to the C <jats:sc>iv</jats:sc> distance that could be used to reveal differences in accretion disk, wind, or corona structure that could be widening the C <jats:sc>iv</jats:sc> EQW–blueshift distribution. A different parameter (such as metallicity) not traced by these data must come into play.</jats:p>
Keywords
310, Galaxies and Cosmology
Sponsorship
National Aeronautics and Space Administration (NASA) (NAS5- 26555)
National Aeronautics and Space Administration (NASA) (G07-18110X)
NSF ∣ National Science Board (NSB) (1908716)
Identifiers
apjac6a5d, ac6a5d, aas34985
External DOI: https://doi.org/10.3847/1538-4357/ac6a5d
This record's URL: https://www.repository.cam.ac.uk/handle/1810/337834
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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