J/ApJ/854/160 SDSS and DES long-term extreme variability QSOs (Rumbaugh+, 2018)
Extreme variability quasars from the Sloan Digital Sky Survey and the Dark
Energy Survey.
Rumbaugh N., Shen Y., Morganson E., Liu X., Banerji M., McMahon R.G.,
Abdalla F.B., Benoit-Levy 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.,
Garcia-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., Wester W.
<Astrophys. J., 854, 160 (2018)>
=2018ApJ...854..160R 2018ApJ...854..160R
ADC_Keywords: QSOs; Surveys; Photometry, SDSS; Redshifts; Spectroscopy
Keywords: black hole physics ; galaxies: active ; line: profiles ;
quasars: general ; surveys
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 Lbol∼1045-1047erg/s and
L/LEdd∼0.01-1. Accounting for selection effects, we estimate an
intrinsic EVQ fraction of ∼30%-50% among all g≲22 quasars over a
baseline of ∼15yr. 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.
Description:
To search for long-term extreme variability quasars (EVQs) we start
from the SDSS DR7 quasar catalog (DR7Q, Schneider+ 2010, VII/260) and
identify counterparts in the regions overlapping with the Dark Energy
Survey (DES) Year-3 imaging data spanning 2013 August to 2016 February
(Flaugher 2005IJMPA..20.3121F 2005IJMPA..20.3121F ; Frieman & Dark Energy Survey
Collaboration 2013AAS...22133501F).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 977 The "extreme variability quasar" (EVQ) sample
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
J/AJ/135/2453 : Sample of BL Lac objects from SDSS and FIRST (Plotkin+, 2008)
J/ApJ/699/782 : High-redshift SDSS-DR5 QSOs (Diamond-Stanic+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/AJ/139/390 : Opt. selected BL Lac objects from SDSS-DR7 (Plotkin+, 2010)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/805/122 : X-ray properties of PHL1811 analogs and WLQs (Luo+, 2015)
J/ApJ/817/172 : X-ray Observations of Stripe 82 (LaMassa+, 2016)
J/MNRAS/463/296 : PS1 slow-blue nuclear hypervariables (Lawrence+, 2016)
J/ApJ/821/33 : Broad Hβ emission line in 102 Seyfert (Runco+, 2016)
J/MNRAS/472/273 : OzDES DR1 (Childress+, 2017)
J/AJ/153/107 : Australian Dark Energy Survey (OzDES) QSO catalog (Tie+, 2017)
http://www.sdss.org/ : SDSS home page
http://www.darkenergysurvey.org/ : DES home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Seq [28/105778] Zero based object index of the
DR7 QSO catalog of Shen+ (2011, J/ApJS/194/45)
8- 17 F10.6 deg RAdeg Right ascension, decimal degrees (J2000)
19- 27 F9.6 deg DEdeg Declination, decimal degrees (J2000)
29- 34 F6.4 --- zspec [0.1/4.4] SDSS spectroscopic redshift
36- 43 F8.2 d MJD-lo [51075/57399.1] Modified Julian Date
of faintest epoch, JD-2400000.5 (1)
45- 50 F6.3 mag gmag-lo [16.3/23.1] SDSS g PSF AB magnitude at MJD-lo
52- 56 F5.3 mag e_gmag-lo [0.005/0.2] Uncertainty in gmag-lo
58- 65 F8.2 d MJD-hi [51075/57399.1] Modified Julian Date of
brightest epoch, JD-2400000.5 (1)
67- 72 F6.3 mag gmag-hi [15.2/21.9] SDSS g PSF AB magnitude at MJD-hi
74- 78 F5.3 mag e_gmag-hi [0.003/0.2] Uncertainty in gmag-hi
80- 81 I2 --- fFIRST [-1/2]? FIRST quasar type (2)
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Note (1): MJDs and magnitudes given for the faintest and brightest epochs in
the combined SDSS and DES light curves.
Note (2): FIRST quasar type flag (equivalent to "FIRSTFRTYPE" column in the
catalog of Shen+ 2011, J/ApJS/194/45) as follows:
0 = FIRST undetected
-1 = outside the FIRST footprint
1 = detected in the FIRST radio survey; core-dominant
2 = detected in the FIRST radio survey; lobe-dominant
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Nov-2018