학술논문
SPACE TELESCOPE AND OPTICAL REVERBERATION MAPPING PROJECT. I. ULTRAVIOLET OBSERVATIONS OF THE SEYFERT 1 GALAXY NGC 5548 WITH THE COSMIC ORIGINS SPECTROGRAPH ON HUBBLE SPACE TELESCOPE
Document Type
article
Author
De Rosa, G; Peterson, BM; Ely, J; Kriss, GA; Crenshaw, DM; Horne, Keith; Korista, KT; Netzer, H; Pogge, RW; Arévalo, P; Barth, AJ; Bentz, MC; Brandt, WN; Breeveld, AA; Brewer, BJ; Bontà, E Dalla; De Lorenzo-Cáceres, A; Denney, KD; Dietrich, M; Edelson, R; Evans, PA; Fausnaugh, MM; Gehrels, N; Gelbord, JM; Goad, MR; Grier, CJ; Grupe, D; Hall, PB; Kaastra, J; Kelly, BC; Kennea, JA; Kochanek, CS; Lira, P; Mathur, S; McHardy, IM; Nousek, JA; Pancoast, A; Papadakis, I; Pei, L; Schimoia, JS; Siegel, M; Starkey, D; Treu, T; Uttley, P; Vaughan, S; Vestergaard, M; Villforth, C; Yan, H; Young, S; Zu, Y
Source
The Astrophysical Journal. 806(1)
Subject
Language
Abstract
We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 171 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correlated variability is found in the continuum and broad emission lines, with amplitudes ranging from ∼30% to a factor of two in the emission lines and a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He ii lagging behind the continuum by ∼2.5 days and Ly , C iv , and Si iv lagging by ∼5-6 days. The relationship between the continuum and emission lines is complex. In particular, during the second half of the campaign, all emission-line lags increased by a factor of 1.3-2 and differences appear in the detailed structure of the continuum and emission-line light curves. Velocity-resolved cross-correlation analysis shows coherent structure in lag versus line of sight velocity for the emission lines; the high-velocity wings of C iv respond to continuum variations more rapidly than the line core, probably indicating higher velocity broad-line region clouds at smaller distances from the central engine. The velocity-dependent response of Ly, however, is more complex and will require further analysis.