NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

Misty C. Bentz; Kelly D. Denney; Edward M. Cackett; Matthias Dietrich; Jeffrey K. J. Fogel; Himel Ghosh; Keith D. Horne; Charles Kuehn; Takeo Minezaki; Christopher A. Onken; Bradley M. Peterson; Richard W. Pogge; Vladimir I. Pronik; Douglas O. Richstone; Sergey G. Sergeev; Marianne Vestergaard; Matthew G. Walker; Yuzuru Yoshii

doi:10.1086/516724

NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

Misty C. Bentz, Kelly D. Denney, Edward M. Cackett, Matthias Dietrich, Jeffrey K. J. Fogel, Himel Ghosh, Keith D. Horne, Charles Kuehn, Takeo Minezaki, Christopher A. Onken, Bradley M. Peterson, Richard W. Pogge, Vladimir I. Pronik, Douglas O. Richstone, Sergey G. Sergeev, Marianne Vestergaard, Matthew G. Walker, Yuzuru Yoshii

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Abstract

We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.

Original language	English
Article number	205
Journal	Astrophysical Journal
Volume	662
Issue number	1
ISSN	0004-637X
DOIs	https://doi.org/10.1086/516724
Publication status	Published - 23 Feb 2007

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Bentz, M. C., Denney, K. D., Cackett, E. M., Dietrich, M., Fogel, J. K. J., Ghosh, H., Horne, K. D., Kuehn, C., Minezaki, T., Onken, C. A., Peterson, B. M., Pogge, R. W., Pronik, V. I., Richstone, D. O., Sergeev, S. G., Vestergaard, M., Walker, M. G., & Yoshii, Y. (2007). NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region . Astrophysical Journal, 662(1), [205]. https://doi.org/10.1086/516724

Bentz, MC, Denney, KD, Cackett, EM, Dietrich, M, Fogel, JKJ, Ghosh, H, Horne, KD, Kuehn, C, Minezaki, T, Onken, CA, Peterson, BM, Pogge, RW, Pronik, VI, Richstone, DO, Sergeev, SG, Vestergaard, M, Walker, MG & Yoshii, Y 2007, 'NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region ', Astrophysical Journal, vol. 662, no. 1, 205. https://doi.org/10.1086/516724

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title = "NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region ",

abstract = "We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.",

keywords = "astro-ph",

author = "Bentz, {Misty C.} and Denney, {Kelly D.} and Cackett, {Edward M.} and Matthias Dietrich and Fogel, {Jeffrey K. J.} and Himel Ghosh and Horne, {Keith D.} and Charles Kuehn and Takeo Minezaki and Onken, {Christopher A.} and Peterson, {Bradley M.} and Pogge, {Richard W.} and Pronik, {Vladimir I.} and Richstone, {Douglas O.} and Sergeev, {Sergey G.} and Marianne Vestergaard and Walker, {Matthew G.} and Yuzuru Yoshii",

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TY - JOUR

T1 - NGC 5548 in a Low-Luminosity State

T2 - Implications for the Broad-Line Region

AU - Bentz, Misty C.

AU - Denney, Kelly D.

AU - Cackett, Edward M.

AU - Dietrich, Matthias

AU - Fogel, Jeffrey K. J.

AU - Ghosh, Himel

AU - Horne, Keith D.

AU - Kuehn, Charles

AU - Minezaki, Takeo

AU - Onken, Christopher A.

AU - Peterson, Bradley M.

AU - Pogge, Richard W.

AU - Pronik, Vladimir I.

AU - Richstone, Douglas O.

AU - Sergeev, Sergey G.

AU - Vestergaard, Marianne

AU - Walker, Matthew G.

AU - Yoshii, Yuzuru

PY - 2007/2/23

Y1 - 2007/2/23

N2 - We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.

AB - We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.

KW - astro-ph

U2 - 10.1086/516724

DO - 10.1086/516724

M3 - Journal article

SN - 0004-637X

VL - 662

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 205

ER -

NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

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