Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548

Horne, Keith; De Rosa, G.; Peterson, B. M.; Barth, A. J.; Ely, J.; Fausnaugh, M. M.; Kriss, G. A.; Pei, L.; Bentz, M. C.; Cackett, E. M.; Edelson, R.; Eracleous, M.; Goad, M. R.; Grier, C. J.; Kaastra, J.; Kochanek, C. S.; Krongold, Y.; Mathur, S.; Netzer, H.; Proga, D.; Tejos, N.; Vestergaard, M.; Villforth, C.; Adams, S. M.; Anderson, M. D.; Arévalo, P.; Beatty, T. G.; Bennert, V. N.; Bigley, A.; Bisogni, S.; Borman, G. A.; Boroson, T. A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Brotherton, M.; Brown, J. E.; Brown, J. S.; Canalizo, G.; Carini, M. T.; Clubb, K. I.; Comerford, J. M.; Corsini, E. M.; Crenshaw, D. M.; Croft, S.; Croxall, K. V.; Dalla Bontà, E.; Deason, A. J.; Dehghanian, M.; De Lorenzo-Cáceres, A.; Denney, K. D.; Dietrich, M.; Done, C.; Efimova, N. V.; Evans, P. A.; Ferland, G. J.; Filippenko, A. V.; Flatland, K.; Fox, O. D.; Gardner, E.; Gates, E. L.; Gehrels, N.; Geier, S.; Gelbord, J. M.; Gonzalez, L.; Gorjian, V.; Greene, J. E.; Grupe, D.; Gupta, A.; Hall, P. B.; Henderson, C. B.; Hicks, S.; Holmbeck, E.; Holoien, T. W. -S.; Hutchison, T.; Im, M.; Jensen, J. J.; Johnson, C. A.; Joner, M. D.; Jones, J.; Kaspi, S.; Kelly, P. L.; Kennea, J. A.; Kim, M.; Kim, S.; Kim, S. C.; King, A.; Klimanov, S. A.; Korista, K. T.; Lau, M. W.; Lee, J. C.; Leonard, D. C.; Li, Miao; Lira, P.; Lochhaas, C.; Ma, Zhiyuan; MacInnis, F.; Malkan, M. A.; Manne-Nicholas, E. R.; Mauerhan, J. C. et al.
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The Astrophysical Journal

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In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM campaign by recovering velocity-delay maps for the prominent broad emission lines (Lyα, C IV, He II, and Hβ) in the spectrum of NGC 5548. These are the most detailed velocity-delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He II response inside 5-10 lt-day has a broad single-peaked velocity profile. The Lyα, C IV, and Hβ responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s-1 in the 10-20 lt-day delay range. An incomplete ellipse in the velocity-delay plane is evident in Hβ. We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at R = 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay $\tau =(R/c)(1-\sin i)\approx 5$ days gives the inclination i ≍ 45°. The inferred black hole mass is MBH ≍ 7 × 107 M⊙. In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the "BLR Holiday" identified in previous work. Moreover, a helical "Barber-Pole" pattern, with stripes moving from red to blue across the C IV and Lyα line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.
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