J/MNRAS/514/164 Optical variability of 190 Quasars in S82 region (Stone+, 2022)
Optical variability of quasars with 20-yr photometric light curves.
Stone Z., Shen Y., Burke C.J., Chen Y.-C., Yang Q., Liu X., Gruendl R.A.,
Adamow M., Andrade-oliveira F., Annis J., Bacon D., Bertin E., Bocquet S.,
Brooks D., Burke D.L., Carnero Rosell A., Carrasco Kind M., Carretero J.,
Da Costa L.N., Pereira M.E.S., De Vicente J., Desai S., Diehl H.T.,
Doel P., Ferrero I., Friedel D.N., Frieman J., Garcia-Bellido J.,
Gaztanaga E., Gruen D., Gutierrez G., Hinton S.R., Hollowood D.L.,
Honscheid K., James D.J., Kuehn K., Kuropatkin N., Lidman C., Maia M.A.G.,
Menanteau F., Miquel R., Morgan R., Paz-Chinchon F., Pieres A.,
Plazas Malagon A.A., Rodriguez-Monroy M., Sanchez E., Scarpine V.,
Serrano S., Sevilla-Noarbe I., Smith M., Suchyta E., Swanson M.E.C.,
Tarle G., To C., (the Des Collaboration)
<Mon. Not. R. Astron. Soc. 514, 164-184 (2022)>
=2022MNRAS.514..164S 2022MNRAS.514..164S (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Black holes ; Optical ; Photometry ; Positional data ;
Models
Keywords: surveys - quasars: general - quasars: supermassive black holes
Abstract:
We study the optical gri photometric variability of a sample of 190
quasars within the SDSS Stripe 82 region that have long-term
photometric coverage during ∼1998-2020 with SDSS, PanSTARRS-1, the
Dark Energy Survey, and dedicated follow- up monitoring with Blanco
4m/DECam. With on average ∼200 nightly epochs per quasar per filter
band, we improve the parameter constraints from a Damped Random Walk
(DRW) model fit to the light curves over previous studies with 10-15 yr
baselines and ≲ 100 epochs. We find that the average damping
time-scale τDRW continues to rise with increased baseline,
reaching a median value of ∼750 d (g band) in the rest frame of these
quasars using the 20-yr light curves. Some quasars may have gradual,
long-term trends in their light curves, suggesting that either the DRW
fit requires very long baselines to converge, or that the underlying
variability is more complex than a single DRW process for these
quasars. Using a subset of quasars with better-constrained τDRW
(less than 20 per cent of the baseline), we confirm a weak wavelength
dependence of τDRW ∝ λ0.51±0.20. We further
quantify optical variability of these quasars over days to decades
time-scales using structure function (SF) and power spectrum density
(PSD) analyses. The SF and PSD measurements qualitatively confirm the
measured (hundreds of days) damping time-scales from the DRW fits.
However, the ensemble PSD is steeper than that of a DRW on time-scales
less than ∼ a month for these luminous quasars, and this second break
point correlates with the longer DRW damping time-scale.
Description:
The optical photometric (continuum) variability of quasars encodes
critical information about physical processes within the accretion
disc of a rapidly accreting supermassive black hole (SMBH) that
primarily emits in the rest-frame UV through optical. There has been
significant progress in the past few decades in quantifying the
observed optical variability of quasars with increasing sample sizes
and light-curve quality. The main purpose of this work is to study
optical continuum variability of a sample of quasars with a more
extended 20-yr baseline. This sample represents one of the
best-quality light-curve data sets to study quasar variability, with
hundreds of epochs from SDSS, PS1 and the high-cadence/high-S/N
monitoring from DES, as well as our dedicated follow-up photometric
monitoring with DECam on the CTIO-4m Blanco telescope. We will improve
the DRW measurements using these extended light curves and quantify
the general optical variability properties with SF and PSD analyses,
(i.e section 1 Introduction).
To study optical quasar variability with long-term light curves, we
utilize quasars identified in the SDSS Stripe 82 region (S82), a
nearly 300 deg2 stripe along the celestial equator, imaged by SDSS
from ∼1998 to 2007. In this work, we use the combined light-curve
data from SDSS, PS1, DES, and DECam imaging for 190 spectroscopically
confirmed quasars in SDSS that are within the two DES-deep fields in
S82. These quasars are all within the SDSS DR7 quasar catalogue, with
derived physical properties such as bolometric luminosities and black
hole masses. All of these quasars have observations in the gri bands
for all surveys, so we focus on these three bands for multiwavelength
variability. We regroup all SF,PSD and DRW analysis results and raw
data in tables table1.dat, table1.fits and table2.fits, (i.e see
section 2 for Data and sections 3.1,3.2,3.3 for model fits).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 1014 190 Properties of variability for our quasars sample
in SDSS Stripe 82 region
table1.fits 2880 9414 All properties of variability, light curves, SF,
CARMA model and PSD in g,r,i SDSS bands
table2.fits 2880 366 Compiling ensemble SF and PSD measurements from
10 subsets of our full quasar sample
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See also:
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/854/160 : SDSS and DES long-term extreme variability QSOs
(Rumbaugh+, 2018)
J/ApJ/753/106 : Quasar variability with SDSS and POSS imaging
(MacLeod+, 2012)
J/MNRAS/499/6053 : Indiv. opt. variability of AGNs from MEXSAS2
(Laurenti+, 2020)
J/A+A/627/A33 : Optically variable AGN in COSMOS field (De Cicco+, 2019)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJS/241/34 : The SDSS Reverberation Mapping (SDSS-RM) project
(Shen+, 2019)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+,2016)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 I7 --- ID Database ID for each quasar (DBID) (1)
9- 17 F9.6 deg RAdeg Right ascension (J2000) (RA)
19- 27 F9.6 deg DEdeg Declination (J2000) (DEC)
29- 39 F11.9 --- z Redshift (Z)
41- 52 F12.9 [Msun] log(Mbh) Logarithm of the black hole mass
(logMBH)
54- 64 F11.9 [Msun] e_log(Mbh) Error of the black hole mass log(Mbh)
(logMBH_ERR)
66- 83 F18.15 [10-7W] log(Lbol) Logarithm of the bolometric luminosity
(log_LBOL)
85- 105 F21.19 [10-7W] e_log(Lbol) Error of the bolometric luminosity
(logLBOLERR)
107- 124 F18.16 [d] log(tauObsg) Logarithm of τDRW damping
time-scale of the DRW light curve
model fit in the SDSS g-band observed
frame (logTAUOBS_g)
126- 144 F19.17 [d] e_log(tauObsg) Lower error of log(tauObsg)
(logTAUOBSgERR_L)
146- 164 F19.17 [d] E_log(tauObsg) Upper error of log(tauObsg)
(logTAUOBSgERR_U)
166- 183 F18.16 [d] log(tauRestg) Logarithm of τDRW in the SDSS
g-band rest frame (logTAUREST_g)
185- 203 F19.17 [d] e_log(tauRestg) Lower error of log(tauRestg)
(logTAURESTgERR_L)
205- 223 F19.17 [d] E_log(tauRestg) Upper error of log(tauRestg)
(logTAURESTgERR_U)
225- 244 F20.17 mag log(SigDRWg) The logarithm of σDRW
long-term standard deviation of
variability in SDSS g-band
(logSIGMAg)
246- 264 F19.17 mag e_log(SigDRWg) Lower error of log(SigDRWg)
(logSIGMAgERRL)
266- 284 F19.17 mag E_log(SigDRWg) Upper error of log(SigDRWg)
(logSIGMAgERRU)
286- 304 F19.16 mag log(Signg) Logarithm of Jitter noise term in
SDSS g-band (logJITTERg) (2)
306- 325 F20.18 mag e_log(Signg) Lower error of log(Signg)
(logJITTERgERRL)
327- 346 F20.18 mag E_log(Signg) Upper error of log(Signg)
(logJITTERgERRU)
348- 367 F20.18 mag RMSg The intrinsic RMS variability in the
SDSS g-band σ0,g (SIG0_g) (3)
369- 389 F21.19 mag e_RMSg Error of RMSg (SIG0gERR)
391- 408 F18.13 0.1nm lRestg Rest-frame wavelength the target was
observed in g-band (LAMBDARESTg)
(4)
410- 427 F18.16 [d] log(tauObsr) Logarithm of τDRW damping
time-scale of the DRW light curve
model fit in the SDSS r-band observed
frame (logTAUOBS_r)
429- 447 F19.17 [d] e_log(tauObsr) Lower error of log(tauObsr)
(logTAUOBSrERR_L)
449- 467 F19.17 [d] E_log(tauObsr) Upper error of log(tauObsr)
(logTAUOBSrERR_U)
469- 486 F18.16 [d] log(tauRestr) Logarithm of τDRW in the SDSS
r-band rest frame (logTAUREST_r)
488- 506 F19.17 [d] e_log(tauRestr) Lower error of log(tauRestr)
(logTAURESTrERR_L)
508- 526 F19.17 [d] E_log(tauRestr) Upper error of log(tauRestr)
(logTAURESTrERR_U)
528- 547 F20.17 mag log(SigDRWr) The logarithm of σDRW
long-term standard deviation of
variability in SDSS r-band
(logSIGMAr)
549- 567 F19.17 mag e_log(SigDRWr) Lower error of log(SigDRWr)
(logSIGMArERRL)
569- 587 F19.17 mag E_log(SigDRWr) Upper error of log(SigDRWr)
(logSIGMArERRU)
589- 607 F19.16 mag log(Signr) Logarithm of Jitter noise term in
SDSS r-band (logJITTERr) (2)
609- 628 F20.18 mag e_log(Signr) Lower error of log(Signr)
(logJITTERrERRL)
630- 649 F20.18 mag E_log(Signr) Upper error of log(Signr)
(logJITTERrERRU)
651- 670 F20.18 mag RMSr The intrinsic RMS variability in the
SDSS r-band σ0,r (SIG0_r) (3)
672- 692 F21.19 mag e_RMSr Error of RMSr (SIG0rERR)
694- 711 F18.13 0.1nm lRestr Rest-frame wavelength the target was
observed in r-band (LAMBDARESTr) (4)
713- 730 F18.16 [d] log(tauObsi) Logarithm of τDRW damping
time-scale of the DRW light curve
model fit in the SDSS i-band observed
frame (logTAUOBS_i)
732- 750 F19.17 [d] e_log(tauObsi) Lower error of log(tauObsi)
(logTAUOBSiERR_L)
752- 770 F19.17 [d] E_log(tauObsi) Upper error of log(tauObsr)
(logTAUOBSiERR_U)
772- 789 F18.16 [d] log(tauResti) Logarithm of τDRW in the SDSS
i-band rest frame (logTAUREST_i)
791- 809 F19.17 [d] e_log(tauResti) Lower error of log(tauResti)
(logTAURESTiERR_L)
811- 829 F19.17 [d] E_log(tauResti) Upper error of log(tauResti)
(logTAURESTiERR_U)
831- 850 F20.17 mag log(SigDRWi) The logarithm of σDRW
long-term standard deviation of
variability in SDSS i-band
(logSIGMAi)
852- 870 F19.17 mag e_log(SigDRWi) Lower error of log(SigDRWi)
(logSIGMAiERRL)
872- 890 F19.17 mag E_log(SigDRWi) Upper error of log(SigDRWi)
(logSIGMAiERRU)
892- 910 F19.16 mag log(Signi) Logarithm of Jitter noise term in
SDSS i-band (logJITTERi) (2)
912- 931 F20.18 mag e_log(Signi) Lower error of log(Signi)
(logJITTERiERRL)
933- 952 F20.18 mag E_log(Signi) Upper error of log(Signi)
(logJITTERiERRU)
954- 973 F20.18 mag RMSi The intrinsic RMS variability in the
SDSS i-band σ0,i (SIG0_i) (3)
975- 995 F21.19 mag e_RMSi Error of RMSi (SIG0iERR)
997-1014 F18.13 0.1nm lResti Rest-frame wavelength the target was
observed in i-band (LAMBDARESTi) (4)
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Note (1): IDs from MacLeod et al. 2012ApJ...753..106M 2012ApJ...753..106M, Cat. J/ApJ/753/106.
Note (2): Term to characterize the effect of a white noise floor from unknown
systematic flux errors also called Jitter σn.
Note (3): Calculated using a maximum-likelihood approach described in
Shen et al. 2019ApJS..241...34S 2019ApJS..241...34S, Cat. J/ApJS/241/34.
Note (4): Rest-frame wavelength are mostly in ultraviolet bands due to
cosmologic redshift 1+z values.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 13-Jan-2025