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Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey
Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L bol ∼ 1045-1047 erg s-1 and L/L Edd ∼ 0.01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ∼30%-50% among all quasars over a baseline of ∼15 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.

black hole physics, galaxies: active, line: profiles, quasars: general, surveys
0004-637X
1-14
Rumbaugh, N.
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Shen, Yue
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Morganson, Eric
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Liu, Xin
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Banerji, M.
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McMahon, R.G.
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Abdalla, F.B.
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Bertin, E.
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Capozzi, D.
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Carnero Rosell, A.
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Carrasco Kind, M.
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Maia, M.A.G.
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Schubnell, M.
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Sheldon, E.
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Smith, M.
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Suchyta, E.
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Swanson, M.E.C.
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Rumbaugh, N.
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Shen, Yue
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Morganson, Eric
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Liu, Xin
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Banerji, M.
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McMahon, R.G.
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Abdalla, F.B.
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Benoit-Lévy, A.
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Bertin, E.
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Brooks, D.
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Capozzi, D.
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Carnero Rosell, A.
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Carretero, J.
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Da Costa, L.N.
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Depoy, D.L.
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Desai, S.
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Frieman, J.
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García-Bellido, J.
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Gschwend, J.
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Gutierrez, G.
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Honscheid, K.
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James, D.J.
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Kuehn, K.
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Lima, M.
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Roodman, A.
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Sanchez, E.
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Sheldon, E.
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Smith, M.
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Soares-Santos, M.
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Sobreira, F.
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Suchyta, E.
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Swanson, M.E.C.
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Walker, A.R.
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Wester, W.
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Rumbaugh, N., Shen, Yue, Morganson, Eric, Liu, Xin, Banerji, M., McMahon, R.G., Abdalla, F.B., Benoit-Lévy, A., Bertin, E., Brooks, D., Buckley-Geer, E., Capozzi, D., Carnero Rosell, A., Carrasco Kind, M., Carretero, J., Cunha, C.E., D'Andrea, C.B., Da Costa, L.N., Depoy, D.L., Desai, S., Doel, P., Frieman, J., García-Bellido, J., Gruen, D., Gruendl, R.A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D.J., Kuehn, K., Kuhlmann, S., Kuropatkin, N., Lima, M., Maia, M.A.G., Marshall, J.L., Martini, P., Menanteau, F., Plazas, A.A., Reil, K., Roodman, A., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sheldon, E., Smith, M., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M.E.C., Walker, A.R. and Wester, W. (2018) Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey. The Astrophysical Journal, 854 (2), 1-14. (doi:10.3847/1538-4357/aaa9b6).

Record type: Review

Abstract

We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L bol ∼ 1045-1047 erg s-1 and L/L Edd ∼ 0.01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ∼30%-50% among all quasars over a baseline of ∼15 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.

Full text not available from this repository.

More information

Accepted/In Press date: 12 January 2018
e-pub ahead of print date: 21 February 2018
Keywords: black hole physics, galaxies: active, line: profiles, quasars: general, surveys

Identifiers

Local EPrints ID: 421341
URI: https://eprints.soton.ac.uk/id/eprint/421341
ISSN: 0004-637X
PURE UUID: 380abeed-29a5-46ba-a8ac-f52c73239834
ORCID for M. Smith: ORCID iD orcid.org/0000-0002-3321-1432

Catalogue record

Date deposited: 01 Jun 2018 16:31
Last modified: 15 Aug 2019 00:33

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Contributors

Author: N. Rumbaugh
Author: Yue Shen
Author: Eric Morganson
Author: Xin Liu
Author: M. Banerji
Author: R.G. McMahon
Author: F.B. Abdalla
Author: A. Benoit-Lévy
Author: E. Bertin
Author: D. Brooks
Author: E. Buckley-Geer
Author: D. Capozzi
Author: A. Carnero Rosell
Author: M. Carrasco Kind
Author: J. Carretero
Author: C.E. Cunha
Author: C.B. D'Andrea
Author: L.N. Da Costa
Author: D.L. Depoy
Author: S. Desai
Author: P. Doel
Author: J. Frieman
Author: J. García-Bellido
Author: D. Gruen
Author: R.A. Gruendl
Author: J. Gschwend
Author: G. Gutierrez
Author: K. Honscheid
Author: D.J. James
Author: K. Kuehn
Author: S. Kuhlmann
Author: N. Kuropatkin
Author: M. Lima
Author: M.A.G. Maia
Author: J.L. Marshall
Author: P. Martini
Author: F. Menanteau
Author: A.A. Plazas
Author: K. Reil
Author: A. Roodman
Author: E. Sanchez
Author: V. Scarpine
Author: R. Schindler
Author: M. Schubnell
Author: E. Sheldon
Author: M. Smith ORCID iD
Author: M. Soares-Santos
Author: F. Sobreira
Author: E. Suchyta
Author: M.E.C. Swanson
Author: A.R. Walker
Author: W. Wester

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