J/ApJ/753/106 Quasar variability with SDSS and POSS imaging (MacLeod+, 2012)
A description of quasar variability measured using repeated SDSS and POSS
imaging.
MacLeod C.L., Ivezic Z., Sesar B., de Vries W., Kochanek C.S., Kelly B.C.,
Becker A.C., Lupton R.H., Hall P.B., Richards G.T., Anderson S.F.,
Schneider D.P.
<Astrophys. J., 753, 106 (2012)>
=2012ApJ...753..106M 2012ApJ...753..106M (SIMBAD/NED BibCode)
ADC_Keywords: QSOs; Photometry, SDSS; Surveys
Keywords: quasars: general
Abstract:
We provide a quantitative description and statistical interpretation
of the optical continuum variability of quasars. The Sloan Digital Sky
Survey (SDSS) has obtained repeated imaging in five UV-to-IR
photometric bands for 33,881 spectroscopically confirmed quasars.
About 10,000 quasars have an average of 60 observations in each band
obtained over a decade along Stripe 82 (S82), whereas the remaining
∼25,000 have 2-3 observations due to scan overlaps. The observed time
lags span the range from a day to almost 10 years, and constrain
quasar variability at rest-frame time lags of up to 4 years, and at
rest-frame wavelengths from 1000Å to 6000Å. We publicly release
a user-friendly catalog of quasars from the SDSS Data Release 7 that
have been observed at least twice in SDSS or once in both SDSS and the
Palomar Observatory Sky Survey, and we use it to analyze the ensemble
properties of quasar variability. Based on a damped random walk (DRW)
model defined by a characteristic timescale and an asymptotic
variability amplitude that scale with the luminosity, black hole mass,
and rest wavelength for individual quasars calibrated in S82, we can
fully explain the ensemble variability statistics of the non-S82
quasars such as the exponential distribution of large magnitude
changes. All available data are consistent with the DRW model as a
viable description of the optical continuum variability of quasars on
timescales of ∼5-2000 days in the rest frame. We use these models to
predict the incidence of quasar contamination in transient surveys
such as those from the Palomar Transient Factory and Large Synoptic
Survey Telescope.
Description:
We define a quasar as any object listed in the SDSS catalog of
spectroscopically confirmed quasars (the "DR7 Quasar Catalog;"
Schneider+ 2010, VII/260).
While SDSS S82 obtained measurements with time differences of up to
10yrs, longer timescales of up to 50 years can be probed by comparing
the SDSS and the Palomar Observatory Sky Surveys (POSS) catalogs.
See Section 2.3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
northcat.dat 490 33881 *Master Norhtern catalog of quasars with
at least two photometric observations
(master_2obsDR7.dat )
southcat.dat 130 9258 SDSS S82 spectroscopically confirmed quasars;
selected data (DBQSOS82.dat)
lcs_s82/* . 9258 *Individual light curves in ASCII tables for
the SDSS S82 quasars (from QSO_S82.tar.gz)
sdssposs.dat 281 81189 All SDSS DR7 quasars with DPOSS observations
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Note on northcat.dat: The contents of this file are taken from the SDSS Quasar
Catalog V (Schneider+ 2010, VII/260).
Note on lcs_s82/* : One row in files 1072282, 1088546, 1365809 and 1475888
ignored by CDS because MJD∼0.
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See also:
II/266 : QUEST1 200k light curve catalog (Rengstorf+, 2004)
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
J/MNRAS/268/305 : Variability of optically selected quasars (Hook+ 1994)
J/MNRAS/275/1102 : Evolution of quasar luminosity function (Hawkins+ 1995)
J/ApJ/633/638 : Variable quasar sample from SDSS (Wilhite+, 2005)
J/AJ/131/1923 : Known QSOs in the QUEST Variability Survey (Rengstorf+, 2006)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJ/680/169 : SDSS DR5 virial black hole masses (Shen+, 2008)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/701/508 : 5000 AGNs behind the Magellanic clouds (Kozlowski+, 2009)
J/ApJ/716/530 : Mid-IR variability from the SDWFS (Kozlowski+, 2010)
J/A+A/525/A37 : Variability indexes of QSOs in SDSS S82 (Meusinger+, 2011)
J/ApJ/728/26 : QSO selection based on photometric variability (Macleod+, 2011)
J/ApJS/194/22 : Magellanic Quasars Survey: QSOs behind SMC (Kozlowski+, 2011)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/746/27 : Magellanic QSOs Survey. II. AGNs behind LMC (Kozlowski+, 2012)
J/ApJ/794/120 : Sloan Digital Sky Survey coadd. Stripe 82 (Annis+, 2014)
J/ApJ/814/150 : Variability of SDSS broad absorption line QSOs (Wang+, 2015)
J/ApJ/854/160 : SDSS & DES long-term extreme variability QSOs (Rumbaugh+, 2018)
J/ApJ/900/58 : Opt-IR LC compilation of DES Stripe 82 quasars (Yang+, 2020)
http://faculty.washington.edu/ivezic/macleod/qso_dr7/ : QSO time variability
data from large data sets archive
Byte-by-byte Description of file: northcat.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS DR7 Object Designation
(HHMMSS.ss+DDMMSS.s; J2000)
19- 29 F11.6 deg RAdeg Right Ascension in decimal degrees (J2000)
30- 40 F11.6 deg DEdeg Declination in decimal degrees (J2000)
41- 47 F7.4 --- z [0.08/5.5] Redshift
48- 54 F7.3 mag umag [15.5/26.8]?=0 BEST SDSS u band PSF AB
magnitude (G2)
55- 60 F6.3 mag e_umag [0.009/5.5]?=0 Error in umag
61- 67 F7.3 mag gmag [15.4/26.5]?=0 BEST SDSS g band PSF AB
magnitude (G2)
68- 73 F6.3 mag e_gmag [0.004/1.5]?=0 Error in gmag
74- 80 F7.3 mag rmag [15.2/22.6]?=0 BEST SDSS r band PSF AB
magnitude (G2)
81- 86 F6.3 mag e_rmag [0.004/4.8]?=0 Error in rmag
87- 93 F7.3 mag imag [15/22.1]?=0 BEST SDSS i band PSF AB
magnitude (G2)
94- 99 F6.3 mag e_imag [0.005/6]?=0 Error in imag
100- 106 F7.3 mag zmag [14.8/22.7]?=0 BEST SDSS z band PSF AB
magnitude (G2)
107- 112 F6.3 mag e_zmag [0.01/2.3]?=0 Error in zmag
113- 119 F7.3 mag Au [0.02/3] Galactic extinction in u filter (G3)
120- 126 F7.3 [cm-2] logNH [19.7/21.4] Log of Galactic HI column density
127- 133 F7.3 mag F20 [-1/16.4] FIRST Peak 20cm flux density (1)
134- 141 F8.3 --- q_F20 [0/1000] Signal-to-ratio for F20
142- 148 F7.3 arcsec SepSF [0/2] SDSS/FIRST separation
149- 156 F8.3 [ct/s] logCR [-9/-0.1] RASS BSC/FSC full band count
rate (2)
157- 163 F7.3 --- q_logCR [0/24] Signal-to-ratio for logCR
164- 170 F7.3 arcsec SepSR [0/30] SDSS/RASS separation
171- 177 F7.3 mag Jmag [13/18.7]?=0 2MASS J band magnitude (3)
178- 183 F6.3 mag e_Jmag [0.02/0.5]?=0 Error in Jmag
184- 190 F7.3 mag Hmag [12.2/17.7]?=0 2MASS H band magnitude (3)
191- 196 F6.3 mag e_Hmag [0.02/0.6]?=0 Error in Hmag
197- 203 F7.3 mag Ksmag [11.3/17.15]?=0 2MASS Ks band magnitude (3)
204- 209 F6.3 mag e_Ksmag [0.02/0.6]?=0 Error in Kmag
210- 216 F7.3 arcsec SepS2M [0/2] SDSS/2MASS separation
217- 219 I3 --- 2Flg [0/26] 2MASS Flags (4)
220- 227 F8.3 mag iMag [-30.3/-22] Absolute SDSS i band
magnitude (G1)
228- 234 F7.3 mag D(g-i) [-1.4/3.7] The (g-i) color offset (5)
237 I1 --- MFlg Morphology flag (1=extended;
0=point source)
240 I1 --- SciFlg SCIENCEPRIMARY flag (1=is SCIENCEPRIMARY)
243 I1 --- SMFlg [0/3] SDSS MODE flag (6)
246 I1 --- UFlg Uniform target selection flag (1=selected
with final algorithm)
247- 258 I12 --- BFlg [0/573571072] Target selection flag; BEST
261 I1 --- BLow-z Low-z Quasar, color selection only, target
flag (1=targeted)
264 I1 --- BHi-z High-z Quasar, color selection only, target
flag (1=targeted)
267 I1 --- BFTFlg FIRST target flag (1=targeted)
270 I1 --- BRTFlg ROSAT target flag (1=targeted)
273 I1 --- BSerFlg Serendipity target flag (1=targeted)
276 I1 --- BStarFlg Star target flag (1=targeted)
279 I1 --- BGalFlg Galaxy target flag (1=targeted)
280- 285 I6 --- Run [94/7264] SDSS Imaging Run Number for
photometric measurements
286- 291 I6 d MJD-I Modified Julian Date of imaging observation
292- 297 I6 d MJD-S Modified Julian Date of spectroscopic
observation
298- 302 I5 --- Plate Spectroscopic Plate Number
303- 307 I5 --- Fiber Spectroscopic Fiber Number
308- 311 I4 --- ReRun SDSS Photometric Processing Rerun Number
312- 314 I3 --- Camera SDSS Camera Column Number
315- 319 I5 --- Frame SDSS Frame Number
320- 324 I5 --- Object SDSS Object Number
325- 336 I12 --- TFlg Target selection flag; TARGET
339 I1 --- TLow-z Low-z Quasar, color selection only, target
flag (1=targeted)
342 I1 --- THi-z High-z Quasar, color selection only, target
flag (1=targeted)
345 I1 --- TFTFlg FIRST target flag (1=targeted)
348 I1 --- TRTFlg ROSAT target flag (1=targeted)
351 I1 --- TSerFlg Serendipity target flag (1=targeted)
354 I1 --- TStarFlg Star target flag (1=targeted)
357 I1 --- TGalFlg Galaxy target flag (1=targeted)
358- 364 F7.3 mag uTmag ?=0 TARGET SDSS u band PSF magnitude (G2)
365- 370 F6.3 mag e_uTmag ?=0 Error in uTmag
371- 377 F7.3 mag gTmag ?=0 TARGET SDSS g band PSF magnitude (G2)
378- 383 F6.3 mag e_gTmag ?=0 Error in gTmag
384- 390 F7.3 mag rTmag ?=0 TARGET SDSS r band PSF magnitude (G2)
391- 396 F6.3 mag e_rTmag ?=0 Error in rTmag
397- 403 F7.3 mag iTmag ?=0 TARGET SDSS i band PSF magnitude (G2)
404- 409 F6.3 mag e_iTmag ?=0 Error in iTmag
410- 416 F7.3 mag zTmag ?=0 TARGET SDSS z band PSF magnitude (G2)
417- 422 F6.3 mag e_zTmag ?=0 Error in zTmag
426- 443 I18 --- ObjID BEST object ID; 64-bit integer
447- 464 I18 --- SpecID Spectroscopic Object ID; 64-bit integer
465- 490 A26 --- Name Previously published name (7)
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Note (1): As AB magnitude where AB mag = -2.5 log_10 [f_nu / 3631 Jy].
0.000 = no detection;
-1.000 = not in FIRST survey area.
Note (2): X-ray data from ROSAT All Sky Survey Bright and Faint source catalogs
-9.000 = no detection.
Note (3): All 2MASS data are from the 2MASS All-Sky Data Release Point Source
Catalog (PSC) 2003 March 25. Note that 2MASS measurements are
Vega-based, not AB, magnitudes.
Note (4): Where 2Flgs = 9*JFLAG+3*HFLAG+KFLAG Individual filter flags:
0 = No Detection;
1 = Catalog Match;
2 = New Photometry on Images.
Note (5): In magnitudes of the quasar (g-i) from the mode of the distribution
of (g-i) of quasars at this redshift. A value of -9.0 indicates too
few quasars at redshift to form mean relation. All colors corrected
for Galactic extinction.
Note (6): for blends, overlapping scans.
1 = Primary object;
2 = Secondary observation;
3 = Family observation.
Note (7): "SDSS" in this column indicates that the object is a previously
published SDSS discovery.
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Byte-by-byte Description of file: southcat.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- DBID [70/7913279] Internal identifier (Name of
the light curve file)
10- 19 F10.6 deg RAdeg Median right ascension (J2000)
23- 31 F9.6 deg DEdeg Median declination (J2000)
34- 38 I5 --- SDR5ID [1/77429]?=-1 Row of DR5 Quasar Catalog IV
(Schneider+ 2007, VII/252)
41- 47 F7.3 mag iMag [-29.6/-22] Absolute i band magnitude (G1)
50- 56 F7.3 mag iMagc [-30.07/-1] Corrected absolute i-band
magnitude; K-corrected to z=2 (1)
59- 64 F6.4 --- z [0.08/5.09] Redshift
68- 73 F6.3 [Msun] MBH [-1/10.97]?=0 log of black hole mass (1)
77- 82 F6.3 [10-7W] logLbol [-1/47.9]?=0 Log of bolometric luminosity
in erg/s (1)
85- 90 F6.3 mag umag [15.54/26.27]?=0 SDSS BEST u-band PSF
AB magnitude (G2)
93- 98 F6.3 mag gmag [15.51/26.04]?=0 SDSS BEST g-band PSF
AB magnitude (G2)
101- 106 F6.3 mag rmag [15.44/22.51]?=0 SDSS BEST r-band PSF
AB magnitude (G2)
109- 114 F6.3 mag imag [15.36/22.09]?=0 SDSS BEST i-band PSF
AB magnitude (G2)
117- 122 F6.3 mag zmag [15.13/22.68]?=0 SDSS BEST z-band PSF
AB magnitude (G2)
126- 130 F5.3 mag Au [0.07/1.81]?=0 Galactic extinction in u
filter (G3)
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Note (1): Taken from the Shen+ (2008, J/ApJ/680/169) catalog. A value of "-1"
indicates a newly confirmed DR7 quasar, and thus is not present in that
catalog (see the latest version, Shen+ 2011, J/ApJS/194/45 for the values).
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Byte-by-byte Description of file: lcs_s82/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 --- MJDu [51075.2/54415.2] Modified Julian Date in u-band
14- 20 F7.3 mag umag [15.1/32]?=-99.99 u-band magnitude
not corrected for Galactic absorption (1)
22- 27 F6.3 mag e_umag [0.001/10]?=99.999 Uncertainty on the umag
29- 40 F12.6 --- MJDg [51075.2/54415.2] Modified Julian Date in g-band
42- 48 F7.3 mag gmag [15.2/32.7]?=-99.99 g-band magnitude
not corrected for Galactic absorption (1)
50- 55 F6.3 mag e_gmag [0.001/9.5]?=99.999 Uncertainty on the gmag
57- 68 F12.6 --- MJDr [51075.2/54415.2] Modified Julian Date in r-band
70- 76 F7.3 mag rmag [15.3/31.7]?=-99.99 r-band magnitude
not corrected for Galactic absorption (1)
78- 83 F6.3 mag e_rmag [0.001/9.7]?=99.999 Uncertainty on the rmag
85- 96 F12.6 --- MJDi [51075.2/54415.2] Modified Julian Date in i-band
98-104 F7.3 mag imag [14.9/33]?=-99.99 i-band magnitude
not corrected for Galactic absorption (1)
106-111 F6.3 mag e_imag [0.001/8.4]?=99.999 Uncertainty on the imag
113-124 F12.6 --- MJDz [51075.2/54415.2] Modified Julian Date in z-band
126-132 F7.3 mag zmag [15/33.7]?=-99.99 z-band magnitude
not corrected for Galactic absorption (1)
134-139 F6.3 mag e_zmag [0.001/10]?=99.999 Uncertainty on the zmag
141-150 F10.6 deg RAdeg [-51/]?=0 Median right ascension (J2000)
152-160 F9.6 deg DEdeg ?=0 Median declination (J2000)
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Note (1): Values ≥99 have been set to -99.99 by CDS.
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Byte-by-byte Description of file: sdssposs.dat
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Bytes Format Units Label Explanations
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1- 13 F13.9 deg RAdeg Right ascension (J2000)
15- 28 F14.11 deg DEdeg [-2.5/70] Declination (J2000)
30- 32 I3 --- Plate [61/894] DPOSS plate identifier
34- 42 F9.4 yr EpochG [1986.11/2000.03] Epoch of the DPOSS
observation in the G band
44- 52 F9.4 yr EpochR [1986.67/1999.87] Epoch of the DPOSS
observation in the R band
54- 63 F10.5 yr EpochI [-123/2000.26] Epoch of the DPOSS
observation in the I band
65- 72 F8.4 mag Gmag [11.6/23.7]?=-99.99 DPOSS G-band magnitude
not corrected for Galactic absorption
74- 84 F11.7 mag e_Gmag [0/2]?=-99.99 Uncertainty on the Gmag
86- 92 F7.5 --- q_Gmag [0/1] Quality of Gmag (1=good) (1)
94- 101 F8.4 mag Rmag [14.2/23]?=-99.99 DPOSS R magnitude
not corrected for Galactic absorption
103- 113 F11.7 mag e_Rmag [0.05/0.7]?=-99.99 Uncertainty on the Rmag
115- 121 F7.5 --- q_Rmag [0/1] Quality of Rmag (1=good) (1)
123- 130 F8.4 mag Imag [10.4/23.1]?=-99.99 DPOSS I band magnitude
not corrected for Galactic absorption
132- 142 F11.7 mag e_Imag [0.06/0.6]?=-99.99 Uncertainty on the Imag
144- 150 F7.5 --- q_Imag [0/1] Quality of Imag (1=good) (1)
152- 157 I6 --- SDR5ID [-32768/32767] Row of DR7 Quasar Catalog V
(Schneider+ 2007, VII/252)
159- 166 F8.4 mag iMag [-30.3/-22] Absolute i-band magnitude (G1)
168- 176 F9.7 --- z [0.078/5.47] Redshift
178- 185 F8.5 Msun MBH [6.9/11.4]?=0 log of black hole mass (2)
187- 194 F8.5 [10-7W] logLbol [44/48.3]?=0 Log of bolometric luminosity
in erg/s (2)
196- 204 F9.7 mag Au [0.015/1.81] Galactic extinction in u
filter (G3)
206- 208 I3 --- Nobs [1/143] Number of observations
210 I1 --- Flag [0/1] Flag for Stripe 82 object
212- 222 F11.5 d MJDr [51075/54210]?=0 Modified Julian Date for SDSS
r-band imaging observation
224- 230 F7.4 mag gmag [15.38/26.42] BEST SDSS g-band PSF AB
magnitude (G2)
232- 241 F10.8 mag e_gmag [0.003/1.22] Uncertainty on the gmag
243- 250 F8.5 mag rmag [15.2/22.4]?=0 BEST SDSS r-band PSF AB
magnitude (G2)
252- 261 F10.8 mag e_rmag [0.003/0.9] Uncertainty on the rmag
263- 270 F8.5 mag imag [14.8/21.91]?=0 BEST SDSS i-band PSF AB
magnitude (G2)
272- 281 F10.8 mag e_imag [0.003/1.1] Uncertainty on the imag
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Note (1): Flag indicating whether the recalibrated magnitude is of good quality
(a value of 1 is "good"). See Sesar+ 2006AJ....131.2801S 2006AJ....131.2801S for a
description of these cuts.
Note (2): Taken from the Shen+ (2011, J/ApJS/194/45) catalog.
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Global notes:
Note (G1): For Ωm=0.300, ΩΛ=0.700, h=0.70, and
aQ=-0.50.
Note (G2): SDSS photometric measurements are asinh magnitudes
(Lupton+ 1999AJ....118.1406L 1999AJ....118.1406L) and are normalized (to ∼3% accuracy)
to the AB-magnitude system (Oke & Gunn 1983ApJ...266..713O 1983ApJ...266..713O).
Uncorrected for Galactic extinction.
Note (G3): Galactic extinction in u filter (from Schlegel+ 1998ApJ...500..525S 1998ApJ...500..525S).
Where Ag, Ar, Ai, Az=0.736, 0.534, 0.405, 0.287 xAu, respectively.
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History:
Downloaded from http://faculty.washington.edu/ivezic/macleod/qso_dr7/
(End) Emmanuelle Perret [CDS] 31-Jan-2022