Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination

S. Collin; T. Kawaguchi; B. M. Peterson; M. Vestergaard

doi:10.1051/0004-6361:20064878

Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination

S. Collin^*, T. Kawaguchi, B. M. Peterson, M. Vestergaard

^*Corresponding author af dette arbejde

343 Citationer (Scopus)

Abstract

Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberationmapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission-line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

Originalsprog	Engelsk
Tidsskrift	Astronomy and Astrophysics
Vol/bind	456
Udgave nummer	1
Sider (fra-til)	75-90
Antal sider	16
ISSN	0004-6361
DOI	https://doi.org/10.1051/0004-6361:20064878
Status	Udgivet - 1 sep. 2006
Udgivet eksternt	Ja

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title = "Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination",

abstract = "Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberationmapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a {"}generalized thick disk{"} model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission-line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.",

keywords = "Galaxies: nuclei, Galaxies: quasars: general, Galaxies: Seyfert",

author = "S. Collin and T. Kawaguchi and Peterson, {B. M.} and M. Vestergaard",

year = "2006",

month = sep,

day = "1",

doi = "10.1051/0004-6361:20064878",

language = "English",

volume = "456",

pages = "75--90",

journal = "Astronomy and Astrophysics Supplement Series",

issn = "0004-6361",

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number = "1",

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TY - JOUR

T1 - Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei

T2 - Eddington ratio and inclination

AU - Collin, S.

AU - Kawaguchi, T.

AU - Peterson, B. M.

AU - Vestergaard, M.

PY - 2006/9/1

Y1 - 2006/9/1

N2 - Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberationmapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission-line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

AB - Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberationmapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission-line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

KW - Galaxies: nuclei

KW - Galaxies: quasars: general

KW - Galaxies: Seyfert

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U2 - 10.1051/0004-6361:20064878

DO - 10.1051/0004-6361:20064878

M3 - Journal article

AN - SCOPUS:33748676635

SN - 0004-6361

VL - 456

SP - 75

EP - 90

JO - Astronomy and Astrophysics Supplement Series

JF - Astronomy and Astrophysics Supplement Series

IS - 1

ER -

Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination

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