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A novel variability-based method for quasar selection: evidence for a rest-frame ∼54 d characteristic time-scale

Graham, Matthew J. and Djorgovski, S. G. and Drake, Andrew J. and Mahabal, Ashish A. and Chang, Melissa and Stern, Daniel and Donalek, Ciro and Glikman, Eilat (2014) A novel variability-based method for quasar selection: evidence for a rest-frame ∼54 d characteristic time-scale. Monthly Notices of the Royal Astronomical Society, 439 (1). pp. 703-718. ISSN 0035-8711. doi:10.1093/mnras/stt2499.

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We compare quasar-selection techniques based on their optical variability using data from the Catalina Real-time Transient Survey (CRTS). We introduce a new technique based on Slepian wavelet variance (SWV) that shows comparable or better performance to structure functions and damped random walk models but with fewer assumptions. Combining these methods with Wide-field Infrared Survey Explorer mid-IR colours produces a highly efficient quasar-selection technique which we have validated spectroscopically. The SWV technique also identifies characteristic time-scales in a time series, and we find a characteristic rest-frame time-scale of ∼54 d, confirmed in the light curves of ∼18 000 quasars from CRTS, SDSS and MACHO data, and anticorrelated with absolute magnitude. This indicates a transition between a damped random walk and P(f) ∝ f^(−1/3) behaviours and is the first strong indication that a damped random walk model may be too simplistic to describe optical quasar variability.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Graham, Matthew J.0000-0002-3168-0139
Djorgovski, S. G.0000-0002-0603-3087
Mahabal, Ashish A.0000-0003-2242-0244
Stern, Daniel0000-0003-2686-9241
Glikman, Eilat0000-0003-0489-3750
Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 December 27. Received 2013 December 19; in original form 2013 November 23. First published online: February 4, 2014. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. We thank the anonymous reviewer for their comments and Debashis Mondal, Donald Percival, Kaspar Schmidt, Nathaniel Butler, Brandon Kelly and Nathalie Palanque-Delabrouille for useful discussions, data and code. We also thank the staff of the Keck and Palomar Observatories for their assistance with observations. This work was supported in part by the NSF grants AST-0909182, IIS-1118041 and AST-1313422, by the W. M. Keck Institute for Space Studies, and by the US Virtual Astronomical Observatory, itself supported by the NSF grant AST-0834235. This work made use of the Million Quasars Catalogue. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the US Department of Energy Office of Science. The SDSS-III website is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University.
Group:Keck Institute for Space Studies
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Keck Institute for Space Studies (KISS)UNSPECIFIED
US Virtual Astronomical ObservatoryUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:methods: data analysis techniques: photometric surveys quasars: general
Issue or Number:1
Record Number:CaltechAUTHORS:20140429-113118628
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Official Citation:Matthew J. Graham, S. G. Djorgovski, Andrew J. Drake, Ashish A. Mahabal, Melissa Chang, Daniel Stern, Ciro Donalek, and Eilat Glikman A novel variability-based method for quasar selection: evidence for a rest-frame ∼54 d characteristic time-scale MNRAS first published online February 4, 2014 doi:10.1093/mnras/stt2499
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45301
Deposited By: Ruth Sustaita
Deposited On:29 Apr 2014 20:41
Last Modified:10 Nov 2021 17:02

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