Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

Pei, L.; Fausnaugh, M.M.; Barth, A.J.; Peterson, B.M.; Bentz, M.C.; De Rosa, G.; Denney, K.D.; Goad, M.R.; Kochanek, C.S.; Korista, K.T.; Kriss, G.A.; Pogge, R.W.; Bennert, V.N.; Brotherton, M.; Clubb, K.I.; Dalla Bontà, E.; Filippenko, A.V.; Greene, J.E.; Grier, C.J.; Vestergaard, M.; Zheng, W.; Adams, S.M.; Beatty, T.G.; Bigley, A.; Brown, J.E.; Brown, J.S.; Canalizo, G.; Comerford, J.M.; Coker, C.T.; Corsini, E.M.; Croft, S.; Croxall, K.V.; Deason, A.J.; Eracleous, M.; Fox, O.D.; Gates, E.L.; Henderson, C.B.; Holmbeck, E.; Holoien, T.W.-S.; Jensen, J.J.; Johnson, C.A.; Kelly, P.L.; Kim, S.; King, A.; Lau, M.W.; Li, M.; Lochhaas, C.; Ma, Z.; Manne-Nicholas, E.R.; Mauerhan, J.C.; Malkan, M.A.; McGurk, R.; Morelli, L.; Mosquera, A.; Mudd, D.; Muller Sanchez, F.; Nguyen, M.L.; Ochner, P.; Ou-Yang, B.; Pancoast, A.; Penny, M.T.; Pizzella, A.; Poleski, R.; Runnoe, J.; Scott, B.; Schimoia, J.S.; Shappee, B.J.; Shivvers, I.; Simonian, G.V.; Siviero, A.; Somers, G.; Stevens, D.J.; Strauss, M...

Abstract

We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multi-wavelength reverberation mapping campaign. The campaign spanned six months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He II λ4686 broad emission-line light curves lag that of the 5100 $\AA$ optical continuum by 4.17+0.36−0.36 days and 0.79+0.35−0.34 days, respectively. The Hβ lag relative to the 1158 $\AA$ ultraviolet continuum light curve measured by the Hubble Space Telescope is roughly ∼50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ∼50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He II λ4686 emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C IV, Ly α, He II(+O III]), and Si IV(+O IV]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the RBLR−LAGN relation based on the past behavior of NGC 5548.

Citation

Pei, L., Fausnaugh, M., Barth, A., Peterson, B., Bentz, M., De Rosa, G., …Zu, Y. (2017). Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548. Astrophysical Journal, 837(2), Article 131. https://doi.org/10.3847/1538-4357/aa5eb1

• Journal Article Type: Article
• Acceptance Date: Feb 3, 2017
• Online Publication Date: Mar 10, 2017
• Publication Date: Mar 10, 2017
• Deposit Date: Feb 20, 2017
• Publicly Available Date: Mar 29, 2017
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 837
• Issue: 2
• Article Number: 131
• DOI: https://doi.org/10.3847/1538-4357/aa5eb1
• Public URL: https://durham-repository.worktribe.com/output/1363562
• Related Public URLs: https://arxiv.org/abs/1702.01177