The Sloan Digital Sky Survey Reverberation Mapping project: Ensemble spectroscopic variability of quasar broad emission lines
- Department of Astronomy and Astrophysics and Institute for Gravitation and the Cosmos, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States)
- Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)
- Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)
- Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
- Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3 (Canada)
- Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)
- SUPA Physics/Astronomy, Univ. of St. Andrews, St. Andrews KY16 9SS, Scotland (United Kingdom)
- Department of Physics, Drexel University, 3141 Chestnut St., Philadelphia, PA 19104 (United States)
- Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, NM, 88349-0059 (United States)
We explore the variability of quasars in the Mg ii and Hβ broad emission lines and ultraviolet/optical continuum emission using the Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic study of quasar variability to date: our study includes 29 spectroscopic epochs from SDSS-RM over 6 months, containing 357 quasars with Mg ii and 41 quasars with Hβ. On longer timescales, the study is also supplemented with two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional 2854 quasars with Mg ii and 572 quasars with Hβ. The Mg ii emission line is significantly variable (Δf/f∼10% on ∼100-day timescales), a necessary prerequisite for its use for reverberation mapping studies. The data also confirm that continuum variability increases with timescale and decreases with luminosity, and the continuum light curves are consistent with a damped random-walk model on rest-frame timescales of ≳5 days. We compare the emission-line and continuum variability to investigate the structure of the broad-line region. Broad-line variability shows a shallower increase with timescale compared to the continuum emission, demonstrating that the broad-line transfer function is not a δ-function. Hβ is more variable than Mg ii (roughly by a factor of ∼1.5), suggesting different excitation mechanisms, optical depths and/or geometrical configuration for each emission line. The ensemble spectroscopic variability measurements enabled by the SDSS-RM project have important consequences for future studies of reverberation mapping and black hole mass estimation of 1
- OSTI ID:
- 22882631
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 811; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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