TY - JOUR
T1 - Studying the [O III]λ5007Å emission-line width in a sample of ~80 local active galaxies
T2 - A surrogate for σ?
AU - Bennert, Vardha N.
AU - Loveland, Donald
AU - Donohue, Edward
AU - Cosens, Maren
AU - Lewis, Sean
AU - Komossa, S.
AU - Treu, Tommaso
AU - Malkan, Matthew A.
AU - Milgram, Nathan
AU - Flatland, Kelsi
AU - Auger, Matthew W.
AU - Park, Daeseong
AU - Lazarova, Mariana S.
N1 - Funding Information:
VNB thanks Dr. Bernd Husemann and Dr. Knud Jahnke for discussions. VNB is grateful to Dr. Hans-Walter Rix and the Max-Planck Institute for Astronomy, Heidelberg, for the hospitality and financial support during her sabbatical stay. VNB, DL, ED, MC, SL, and NM gratefully acknowledge assistance from a National Science Foundation (NSF) Research at Undergraduate Institutions (RUI) grant AST-1312296. Note that findings and conclusions do not necessarily represent views of the NSF. This research has made use of the Dirac computer cluster at Cal Poly, maintained by Dr. Brian Granger and Dr. Ashley Ringer McDonald. Spectra were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among Caltech, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the public archive of the SDSS and the NASA/Infrared Processing and Analysis Center Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Funding Information:
VNB thanks Dr. Bernd Husemann and Dr. Knud Jahnke for discussions. VNB is grateful to Dr. Hans-Walter Rix and the Max-Planck Institute forAstronomy, Heidelberg, for the hospitality and financial support during her sabbatical stay. VNB, DL, ED, MC, SL, andNM gratefully acknowledge assistance from a National Science Foundation (NSF) Research at Undergraduate Institutions (RUI) grant AST-1312296. Note that findings and conclusions do not necessarily represent views of the NSF. This research has made use of the Dirac computer cluster at Cal Poly, maintained by Dr. Brian Granger and Dr. Ashley Ringer McDonald. Spectra were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among Caltech, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the public archive of the SDSS and the NASA/Infrared Processing and Analysis Center Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Publisher Copyright:
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2018/11/21
Y1 - 2018/11/21
N2 - For a sample of ~80 local (0.02 = z = 0.1) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially resolved stellar-velocity dispersion (σ) measurements, we study the profile of the [O III]γ5007Åemission line to test the validity of using its width as a surrogate for σ. Such an approach has often been used in the literature, since it is difficult to measure σ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellarabsorption lines. Fitting the [O III] line with a single Gaussian or Gauss-Hermite polynomials overestimates σ by 50-100 per cent. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width (σ[O III], D) and σ is ~1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-σ[O III], D relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between σ and σ[O III], D shows no close correlation, only that both quantities have the same range, average, and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s-1), our results strongly caution against the use of [O III] width as a surrogate for σ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a ~10 per cent larger [O III] core width.
AB - For a sample of ~80 local (0.02 = z = 0.1) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially resolved stellar-velocity dispersion (σ) measurements, we study the profile of the [O III]γ5007Åemission line to test the validity of using its width as a surrogate for σ. Such an approach has often been used in the literature, since it is difficult to measure σ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellarabsorption lines. Fitting the [O III] line with a single Gaussian or Gauss-Hermite polynomials overestimates σ by 50-100 per cent. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width (σ[O III], D) and σ is ~1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-σ[O III], D relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between σ and σ[O III], D shows no close correlation, only that both quantities have the same range, average, and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s-1), our results strongly caution against the use of [O III] width as a surrogate for σ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a ~10 per cent larger [O III] core width.
KW - Accretion
KW - Accretion discs
KW - Black hole physics
KW - Galaxies: Seyfert
KW - Galaxies: active
KW - Galaxies: evolution
KW - Galaxies: statistics
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U2 - 10.1093/mnras/sty2236
DO - 10.1093/mnras/sty2236
M3 - Article
AN - SCOPUS:85054098813
SN - 0035-8711
VL - 481
SP - 138
EP - 152
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -