black hole masses from reverberation mapping
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Black Hole Masses fromReverberation Mapping
Bradley M. PetersonThe Ohio State University
Collaborators: M. Bentz, S. Collin, K. Dasyra, K. Denney,
L. Ferrarese, K. Horne, S. Kaspi, T. Kawaguchi, C. Kuehn,
D. Maoz, K. Metzroth, T. Minezaki, H. Netzer, C.A. Onken,
R.W. Pogge, S.G. Sergeev, L. Tacconi, M. Vestergaard,
A. Wandel, Y. Yoshii
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Key Points
• The line-width measure used for reverberation-based masses should be the line dispersion line rather than FWHM.
• New observations are leading to improved results, better identification of systematics.
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Reverberation Mapping Results
• Reverberation lags have been measured for 36 AGNs, mostly for one or more Balmer lines, but in some cases for multiple lines.
• AGNs with lags for multiple lines show that highest ionization emission lines respond most rapidly ionization stratification.
Evidence for a Virialized BLR
• Gravity is important– Broad-lines show
virial relationship between size of line-emitting region and line width, r 2
– Yields measurement of black-hole mass
M = f (ccent 2 /G) H Other Lines
based on Peterson & Wandel (1999)
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• Determine scale factor f that matches AGNs to the quiescent-galaxy MBH-*. relationship
• Current best estimate: f = 5.5 ± 1.8
• Scaling factor is empirically determined
• This removes bias from the ensemble– Equal numbers of
masses are overestimated and underestimated
Calibration of the Reverberation Mass Scale
Tremaine slope
Ferrarese slope
based on Onken et al. (2004)
M = f (ccent 2 /G)
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Physical Interpretation of f• The Onken value is an
average over the projection factors.
• Example: thin ring
VP)(sin
2 2
2
ifG
c
iM BH
diiiPiff sin)()(
Aside: since unification requires 0 i imax, simple disks without a polar component are formally ruled out.
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Characterizing Line WidthsFWHM: Trivial to measure Less sensitive to blending
and extended wings
Line dispersion line: Well defined Less sensitive to narrow-line
components More accurate for low-contrast lines
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220
2line / dPdP
line
FWHM
6 2/1)2ln2(2 32 22
2.45 2.833.462.35
Sometrivial
profiles:
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• Reverberation-mapped AGNs show broad range of FWHM/line.• Mass calibration is sensitive to which line-width measure is used!
– Even worse, there is a bias with respect to AGN type (as reflected in the profiles)
NLS1 + I Zw 1-type
NGC 5548 H Extreme examples
NGC 3227
NGC 3516
NGC 4051
I Zw 1 type
NLS1
I Zw 1 type
NLS1
NGC 5548
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Subset of the abovefor which host-galaxyluminosity can beremoved accurately.
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Pop A Pop Bsimilar to Sulentic et al.
Pop 1
Pop 2
Col
lin e
t al
.
From Collin et al. (2006)
Mean spectraRMSspectra
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Pop 1
Pop 2
Pop A Pop Bsimilar to Sulentic et al.
Col
lin e
t al
.
From Collin et al. (2006)
Mean spectraRMSspectra f = 5.7 1.5
f = 5.4 2.7
f = 6.2 3.5f = 4.7 1.1
line-based calibration
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Pop 1
Pop 2
Pop A Pop Bsimilar to Sulentic et al.
Col
lin e
t al
.
From Collin et al. (2006)
Mean spectraRMSspectra f = 0.9 0.3
f = 2.2 1.2
FWHM-based
f = 2.5 1.5f = 0.8 0.2
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Line Width Measures
• Conclusion: line is probably a less biased indicator of the mass than FWHM.
• Use of FWHM will lead us to underestimate the masses of NLS1s, I Zw 1-type objects, and narrower-line objects in general.– Can be corrected for empirically, however
(see Collin, Kawaguchi, Peterson, & Vestergaard 2006).
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HST ACS imagesare used to decomposelight into nuclearand starlight components.
Effect is to flattenradius-luminosityrelationship.
Starlight components are stronger than previously supposed.
Bentz et al. (2006)
Other New Developments
• New reverberation program on bright well-known Seyfert galaxies– Improve time sampling
interval over original programs by as much as an order of magnitude in some cases.
– Ultimate goal: a velocity-delay map for at least one line in one AGN.
– Secondary goal: improve black hole mass measurements.
Denney et al., in preparation
Bentz et al., in preparation
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NGC 4151• Reanalyzed two
UV monitoring data sets from IUE archive.
• UV and optical give consistent mass, 5 107 M
C IV (upper limit)Other UV linesNew H result
Metzroth, Onken, & Peterson (2006)Bentz et al., in preparation
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NGC 4151• Moreover, the
reverberation-based mass is consistent with the (highly uncertain) stellar dynamical mass based on long-slit spectra of the Ca II triplet.
Onken, Valluri, et al.,in preparation
Mrev
AGNs: Ca II triplet
AGNs: CO bandhead(Dasyra & Tacconi)
Quiescent: (Tremaine et al. 2002)
The AGN MBH – * Relationship
Onken calibration
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Could Inclination Play a Role?
• Assume line width V (a2 + sin2i )1/2 Vkep
• Then f M / VP 1 / (a2 + sin2i )1/2
• M / VP cannot be used to deduce inclination for individual sources because NGC 5548 shows that VP values can span a factor ~3.
Collin et al. (2006)
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Could Inclination Play a Role?
• However, we can compare the OBSERVED cumulative distribution of M / VP with that predicted by this simple model for various values of a.
• Reasonable agreement with simple model if only Population 1/A is used.– Implication is that at least
some AGNs have narrow lines because of low inclination.
Collin et al. (2006)
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Summary
• As the database on reverberation mapped AGNs improves, identification of systematic biases becomes easier.– Evidence that inclination plays a role.
• Reverberation-masses are less biased with respect to profile by using line as the line-width measure.– FWHM / line is sensitive to Eddington rate
and inclination.
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What Do Line Widths Say About Masses?
BHMmML
4/1
2
4/1
BH
2/1
2/1BH
BH
2/1
2/1BH
2/1
BLR
BH
)(
m
L
m
M
Mm
M
L
M
R
MV
2BLRBH VRM 2/1
BLR LR
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Brad’s gripe du jour:
4/1
2
4/1
BH
m
L
m
MV
• For fixed Eddington rate, more massive sources have larger line widths:– NLS1 criterion of FWHM < 2000 km s-1
omits higher-luminosity objects from class (“I Zw 1–type” objects, including, for example, 3C 273)
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