Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

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

Research output: Contribution to journalReview articlepeer-review


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.

Original languageEnglish (US)
Article number160
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 20 2018


  • black hole physics
  • galaxies: active
  • line: profiles
  • quasars: general
  • surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey'. Together they form a unique fingerprint.

Cite this