Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broadband Time Delays in NGC 5548
journal contribution
posted on 2016-03-31, 14:03 authored by M. M. Fausnaugh, K. D. Denney, A. J. Barth, M. C. Bentz, M. C. Bottorff, M. T. Carini, K. V. Croxall, G. De Rosa, M. R. Goad, K. Horne, M. D. Joner, S. Kaspi, M. Kim, S. A. Klimanov, C. S. Kochanek, D. C. Leonard, H. Netzer, B. M. Peterson, K. Schnülle, S. G. Sergeev, M. Vestergaard, W.-K. Zheng, Y. Zu, M. D. Anderson, P. Arévalo, C. Bazhaw, G. A. Borman, T. A. Boroson, W. N. Brandt, A. A. Breeveld, B. J. Brewer, E. M. Cackett, D. M. Crenshaw, E. Dalla Bontà, A. De Lorenzo-Cáceres, M. Dietrich, R. Edelson, N. V. Efimova, J. Ely, P. A. Evans, A. V. Filippenko, K. Flatland, N. Gehrels, S. Geier, J. M. Gelbord, L. Gonzalez, V. Gorjian, C. J. Grier, D. Grupe, P. B. Hall, S. Hicks, D. Horenstein, T. Hutchison, M. Im, J. J. Jensen, J. Jones, J. Kaastra, B. C. Kelly, J. A. Kennea, S. C. Kim, K. T. Korista, G. A. Kriss, J. C. Lee, P. Lira, F. Macinnis, E. R. Manne-Nicholas, S. Mathur, I. M. Mchardy, C. Montouri, R. Musso, S. V. Nazarov, R. P. Norris, J. A. Nousek, D. N. Okhmat, A. Pancoast, I. Papadakis, J. R. Parks, L. Pei, R. W. Pogge, J.-U. Pott, S. E. Rafter, H.-W. Rix, D. A. Saylor, J. S. Schimoia, M. Siegel, M. Spencer, D. Starkey, H.-I. Sung, K. G. Teems, T. Treu, C. S. Turner, P. Uttley, C. Villforth, Y. Weiss, J.-H. Woo, H. Yan, S. YoungWe present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength
reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January
to July in nine filters (BVRI and ugriz). Combined with ultraviolet data from the Hubble Space Telescope and
Swift, we confirm significant time delays between the continuum bands as a function of wavelength, extending
the wavelength coverage from 1158 Å to the z band (∼9160 Å). We find that the lags at wavelengths longer than
the V band are equal to or greater than the lags of high-ionization-state emission lines (such as He II λ1640 and
λ4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line
region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing
by an accretion disk with τ ∝ λ
4/3
. However, the lags also imply a disk radius that is 3 times larger than
the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10% of the Eddington
luminosity (L = 0.1LEdd). Using optical spectra from the Large Binocular Telescope, we estimate the bias of
the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with
high levels of BLR contamination (∼20%) can be important for the shortest continuum lags, and likely has a
significant impact on the u and U bands owing to Balmer continuum emission.
Funding
The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia; The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University. This paper used data obtained with the MODS spectrographs built with funding from National Science Foundation (NSF) grant AST-9987045 and the NSF Telescope System Instrumentation Program (TSIP), with additional funds from the Ohio Board of Regents and the Ohio State University Office of Research. This paper made use of the modsIDL spectral data reduction pipeline developed in part with funds provided by NSF Grant AST - 1108693. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia and Jim Katzman Foundation, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. Support for HST program number GO-13330 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. M.M.F., G.D.R., B.M.P., C.J.G., and R.W.P. are grateful for the support of the NSF through grant AST- 1008882 to The Ohio State Uni
History
Citation
The Astrophysical Journal, 2016, 821(1)Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and AstronomyVersion
- VoR (Version of Record)
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The Astrophysical JournalPublisher
American Astronomical Societyissn
2041-8205eissn
2041-8213Copyright date
2016Available date
2016-03-31Publisher DOI
Publisher version
http://iopscience.iop.org/article/10.3847/0004-637X/821/1/56/metaLanguage
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