J/ApJ/905/52 Extreme variability QSOs from SDSS DR16 (Guo+, 2020)
High-redshift extreme variability quasars from Sloan Digital Sky Survey
multiepoch spectroscopy.
Guo H., Peng J., Zhang K., Burke C.J., Liu X., Sun M., Wang S., Kong M.,
Sheng Z., Wang T., He Z., Gu M.
<Astrophys. J., 905, 52 (2020)>
=2020ApJ...905...52G 2020ApJ...905...52G
ADC_Keywords: QSOs; Spectra, optical; Redshifts; Equivalent widths; Black holes;
Radio sources
Keywords: Active galactic nuclei ; Quasars ; Black hole physics ;
Spectroscopy ; Time domain astronomy
Abstract:
We perform a systematic search for high-redshift (z>1.5) extreme
variability quasars (EVQs) using repeat spectra from the Sixteenth
Data Release of the Sloan Digital Sky Survey, which provides a
baseline spanning up to ∼18yr in the observed frame. We compile a
sample of 348 EVQs with a maximum continuum variability at rest frame
1450Å of more than 100% (i.e., δV=(Max-Min)/Mean>1). The EVQs
show a range of emission-line variability, including 23 where at least
one line in our redshift range disappears below detectability, which
can then be seen as analogous to low-redshift changing-look quasars
(CLQs). Importantly, spurious CLQs caused by problematic SDSS spectral
flux calibration, e.g., fiber-drop issue, have been rejected. The
similar properties (e.g., continuum/line, difference-composite spectra
and Eddington ratio) of normal EVQs and CLQs imply that they are
basically the same physical population with analogous intrinsic
variability mechanisms, as a tail of a continuous distribution of
normal quasar properties. In addition, we find no reliable evidence
(≤1σ) to support that CLQs are a subset of EVQs with less
efficient accretion. Finally, we also confirm the antibreathing of CIV
(i.e., the line width increases as luminosity increases) in EVQs and
find that in addition to the ∼0.4dex systematic uncertainty in
single-epoch CIV virial black hole mass estimates, an extra scatter of
∼0.3dex will be introduced by extreme variability.
Description:
All the spectra in this work are obtained from the public Sixteenth
Data Release of Sloan Digital Sky Survey (SDSS DR16) database
(Ahumada+, 2020, V/154).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 189 696 Catalog
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See also:
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/ApJ/633/638 : Variable quasar sample from SDSS (Wilhite+, 2005)
J/ApJS/166/470 : SDSS-Spitzer type I QSOs IR photometry (Richards+, 2006)
J/ApJ/641/78 : CIV variability in 105 SDSS quasars (Wilhite+, 2006)
J/ApJ/679/962 : Quasars with strong nitrogen emission lines (Jiang+, 2008)
J/ApJ/680/169 : SDSS DR5 virial black hole masses (Shen+, 2008)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)
J/ApJ/753/125 : NIR spectroscopy follow-up of 60 SDSS-DR7 QSOs (Shen+, 2012)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/789/140 : SDSS quasars balmer emission lines (Liu+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/217/26 : Lick AGN monitoring 2011: light curves (Barth+, 2015)
J/ApJS/216/4 : SDSS-RM project: technical overview (Shen+, 2015)
J/ApJ/821/33 : Broad Hβ emission line in Seyfert galaxies (Runco+, 2016)
J/ApJ/859/8 : SDSS J120414.37+351800.5 quasar opt. photometry (Liu+, 2018)
J/ApJ/854/160 : SDSS&DES long-term extreme variability QSOs (Rumbaugh+, 2018)
J/ApJ/874/8 : Follow-up sp. of SDSS changing-look QSOs (Macleod+, 2019)
J/ApJS/241/34 : The SDSS Reverberation Mapping (SDSS-RM) project (Shen+, 2019)
J/ApJ/883/94 : Optical and UV follow-up of 1ES 1927+654 (Trakhtenbrot+, 2019)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- GroupID [10859/292717] SDSS DR16 repeat catalog
object identifier
8- 12 I5 --- Plate [309/11703] SDSS spectroscopic plate number
14- 18 I5 d MJD [51792/58543] Modified Julian Date of
spectroscopic observation
20- 23 I4 --- Fiber [2/1000] SDSS spectroscopic fiber number
25- 34 F10.6 deg RAdeg Right Ascension (J2000)
36- 44 F9.6 deg DEdeg [-8.5/65.6] Declination (J2000)
46- 50 F5.3 --- z [1.5/4] Spectroscopic redshift
52- 53 I2 --- Nep [2/23] Number of spectroscopic observations
55- 56 I2 --- FIRST [-1/1] FIRST detection code (1=detected;
-1=out of FIRST footprint)
58- 64 F7.3 mJy F1.4GHz [0.7/160]?=-1 Observed FIRST 20cm flux
density
66- 67 I2 --- Flag [-1/1] Brightest/faintest epoch flag
(1=brightest or -1=faintest epoch)
69- 73 F5.3 --- 1450avg [1/2.1] Rest frame 1450Å continuum
variability (1)
75- 81 F7.3 cW/m2/nm F1450 [-0.007/122] Rest frame 1450Å flux
density; erg/s/cm2/Å
83- 88 F6.3 --- SN1450 [-0.012/26] Signal-to-Noise at 1450Å
90- 95 F6.3 --- SNCIV [0.1/57.2] Signal-to-Noise of CIV line
97- 102 F6.3 [10-7W] L1350 [-1/47.2] Log monochromatic 1350Å
luminosity; erg/s
104- 109 F6.3 [10-7W] e_L1350 [0/0.3]?=-1 Uncertainty in L1350
111- 119 F9.3 km/s FWHM-civ [1199/13274] Whole CIV line Full-Width at
Half-Maximum
121- 128 F8.3 km/s e_FWHM-civ [0.2/7636]?=-1 Uncertainty in FWHM-civ
130- 136 F7.3 0.1nm EW-civ [13.6/283.8] Rest frame broad CIV
equivalent width; in Angstroms
138- 143 F6.3 0.1nm e_EW-civ [0/89.6]?=-1 Uncertainty in EW-civ
145- 150 F6.3 [Msun] BH-civ [7.2/9.8]?=-1 Log virial BH mass
from CIV (2)
152- 157 F6.3 [Msun] e_BH-civ [0.001/1.2]?=-1 Uncertainty in BH-civ
159- 164 F6.3 [Msun] BH-mean [7.4/10]?=-1 Log adopted fiducial virial BH
mass (3)
166- 171 F6.3 [Msun] e_BH-mean [0.002/1.2]?=-1 Uncertainty in BH-mean
173- 180 F8.3 [-] LogEdd [-2.1/0.3]?=-999 Log Eddington ratio based
on logMBHa
182- 187 F6.3 --- chi2 [1.4/33] Reduced χ2 for CIV line
fitting
189 I1 --- Type [0/1] Type (0=changing-look quasar (CLQ);
1=extreme variability quasar (EVQ),
650 occurrences)
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Note (1): Where Var=(Max-Min)/[0.5(Max+Min)].
Note (2): Calibration of Vestergaard & Peterson (2006ApJ...641..689V 2006ApJ...641..689V).
Note (3): MBH=0.5(Mbright+Mfaint).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-May-2022