Studying the [O III]λ5007Å emission-line width in a sample of ~80 local active galaxies

A surrogate for σ?

Vardha N. Bennert, Donald Loveland, Edward Donohue, Maren Cosens, Sean Lewis, S. Komossa, Tommaso Treu, Matthew A. Malkan, Nathan Milgram, Kelsi Flatland, Matthew W. Auger, Daeseong Park, Mariana Lazarova

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)138-152
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume481
Issue number1
DOIs
StatePublished - Nov 21 2018

Fingerprint

active galaxies
radio
asymmetry
active galactic nuclei
kinematics
gas
galaxies
deviation
reverberation
profiles
gravitational fields
slits
standard deviation
polynomials
luminosity
distribution
comparison
test
continuums

Keywords

  • Accretion
  • Accretion discs
  • Black hole physics
  • Galaxies: Seyfert
  • Galaxies: active
  • Galaxies: evolution
  • Galaxies: statistics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Studying the [O III]λ5007Å emission-line width in a sample of ~80 local active galaxies : A surrogate for σ? / Bennert, Vardha N.; Loveland, Donald; Donohue, Edward; Cosens, Maren; Lewis, Sean; Komossa, S.; Treu, Tommaso; Malkan, Matthew A.; Milgram, Nathan; Flatland, Kelsi; Auger, Matthew W.; Park, Daeseong; Lazarova, Mariana.

In: Monthly Notices of the Royal Astronomical Society, Vol. 481, No. 1, 21.11.2018, p. 138-152.

Research output: Contribution to journalArticle

Bennert, VN, Loveland, D, Donohue, E, Cosens, M, Lewis, S, Komossa, S, Treu, T, Malkan, MA, Milgram, N, Flatland, K, Auger, MW, Park, D & Lazarova, M 2018, 'Studying the [O III]λ5007Å emission-line width in a sample of ~80 local active galaxies: A surrogate for σ?', Monthly Notices of the Royal Astronomical Society, vol. 481, no. 1, pp. 138-152. https://doi.org/10.1093/mnras/sty2236
Bennert, Vardha N. ; Loveland, Donald ; Donohue, Edward ; Cosens, Maren ; Lewis, Sean ; Komossa, S. ; Treu, Tommaso ; Malkan, Matthew A. ; Milgram, Nathan ; Flatland, Kelsi ; Auger, Matthew W. ; Park, Daeseong ; Lazarova, Mariana. / Studying the [O III]λ5007Å emission-line width in a sample of ~80 local active galaxies : A surrogate for σ?. In: Monthly Notices of the Royal Astronomical Society. 2018 ; Vol. 481, No. 1. pp. 138-152.
@article{6f0f037362bf49b9ae6ca7c406072d9d,
title = "Studying the [O III]λ5007{\AA} emission-line width in a sample of ~80 local active galaxies: A surrogate for σ?",
abstract = "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]γ5007{\AA}emission 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.",
keywords = "Accretion, Accretion discs, Black hole physics, Galaxies: Seyfert, Galaxies: active, Galaxies: evolution, Galaxies: statistics",
author = "Bennert, {Vardha N.} and Donald Loveland and Edward Donohue and Maren Cosens and Sean Lewis and S. Komossa and Tommaso Treu and Malkan, {Matthew A.} and Nathan Milgram and Kelsi Flatland and Auger, {Matthew W.} and Daeseong Park and Mariana Lazarova",
year = "2018",
month = "11",
day = "21",
doi = "10.1093/mnras/sty2236",
language = "English (US)",
volume = "481",
pages = "138--152",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",

}

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

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

UR - http://www.scopus.com/inward/record.url?scp=85054098813&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85054098813&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty2236

DO - 10.1093/mnras/sty2236

M3 - Article

VL - 481

SP - 138

EP - 152

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 1

ER -