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

Horne, Keith and Rosa, G. De and Peterson, B. M. and Barth, A. J. and Ely, J. and Fausnaugh, M. M. and Kriss, G. A. and Pei, L. and Bentz, M. C. and Cackett, E. M. and Edelson, R. and Eracleous, M. and Goad, M. R. and Grier, C. J. and Kaastra, J. and Kochanek, C. S. and Krongold, Y. and Mathur, S. and Netzer, H. and Proga, D. and Tejos, N. and Vestergaard, M. and Villforth, C. and Adams, S. M. and Anderson, M. D. and Arévalo, P. and Beatty, T G. and Bennert, V. N. and Bigley, A. and Bisogni, S. and Borman, G. A. and Boroson, T. A. and Bottorff, M. C. and Brandt, W. N. and Breeveld, A. A. and Brotherton, M. and Brown, J. E. and Brown, J. S. and Canalizo, G. and Carini, M. T. and Clubb, K. I. and Comerford, J. M. and Corsini, E. M. and Crenshaw, D. M. and Croft, S. and Croxall, K. V. and Bontà, E. Dalla and Deason, A. J. and Dehghanian, M. and Lorenzo-Cáceres, A. De and Denney, K. D. and Dietrich, M. and Done, C. and Efimova, N. V. and Evans, P. A. and Ferland, G. J. and Filippenko, A. V. and Flatland, K. and Fox, O. D. and Gardner, E. and Gates, E. L. and Gehrels, N. and Geier, S. and Gelbord, J. M. and Gonzalez, L. and Gorjian, V. and Greene, J. E. and Grupe, D. and Gupta, A. and Hall, P. B. and Henderson, C. B. and Hicks, S. and Holmbeck, E. and Holoien, T. W.-S. and Hutchison, T. and Im, M. and Jensen, J. J. and Johnson, C. A. and Joner, M. D. and Jones, J. and Kaspi, S. and Kelly, P. L. and Kennea, J. A. and Kim, M. and Kim, S. and Kim, S. C. and King, A. and Klimanov, S. A. and Korista, K. T. and Lau, M. W. and Lee, J. C. and Leonard, D. C. and Li, Miao and Lira, P. and Lochhaas, C. and Ma, Zhiyuan and MacInnis, F. and Malkan, M. A. and Manne-Nicholas, E. R. and Mauerhan, J. C. and McGurk, R. and McHardy, I. M. and Montuori, C. and Morelli, L. and Mosquera, A. and Mudd, D. and Müller–Sánchez, F. and Nazarov, S. V. and Norris, R. P. and Nousek, J. A. and Nguyen, M. L. and Ochner, P. and Okhmat, D. N. and Pancoast, A. and Papadakis, I. and Parks, J. R. and Penny, M. T. and Pizzella, A. and Pogge, R. W. and Poleski, R. and Pott, J.-U. and Rafter, S. E. and Rix, H.-W. and Runnoe, J. and Saylor, D. A. and Schimoia, J. S. and Schnülle, K. and Scott, B. and Sergeev, S. G. and Shappee, B. J. and Shivvers, I. and Siegel, M. and Simonian, G. V. and Siviero, A. and Skielboe, A. and Somers, G. and Spencer, M. and Starkey, D. and Stevens, D. J. and Sung, H.-I. and Tayar, J. and Treu, T. and Turner, C. S. and Uttley, P. and Van Saders, J. and Vican, L. and Villanueva, S. and Weiss, Y. and Woo, J.-H. and Yan, H. and Young, S. and Yuk, H. and Zheng, W. and Zhu, W. and Zu, Y. (2021) 'Space Telescope and Optical Reverberation Mapping Project. IX. Velocity–Delay Maps for Broad Emission Lines in NGC 5548.', The astrophysical journal., 907 (2). p. 76.


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.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Publisher statement:This is an author-created, un-copyedited version of an article published in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at
Date accepted:25 November 2020
Date deposited:22 July 2021
Date of first online publication:01 February 2021
Date first made open access:01 February 2022

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