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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)