J/AJ/134/973 SDSS Stripe 82 star catalogs (Ivezic+, 2007)
Sloan Digital Sky Survey standard star catalog for stripe 82: the dawn of
industrial 1% optical photometry.
Ivezic Z., Smith J.A., Miknaitis G., Lin H., Tucker D., Lupton R.H.,
Gunn J.E., Knapp G.R., Strauss M.A., Sesar B., Doi M., Tanaka M.,
Fukugita M., Holtzman J., Kent S., Yanny B., Schlegel D., Finkbeiner D.,
Padmanabhan N., Rockosi C.M., Juric M., Bond N., Lee B., Stoughton C.,
Jester S., Harris H., Harding P., Morrison H., Brinkmann J.,
Schneider D.P., York D.
<Astron. J., 134, 973-998 (2007)>
=2007AJ....134..973I 2007AJ....134..973I
ADC_Keywords: Photometry, SDSS ; Stars, variable ; QSOs ; Surveys
Keywords: Catalogs; Instrumentation: Photometers; Methods: Data Analysis;
Standards; Surveys; Techniques: Photometric
Abstract:
We describe a standard star catalog constructed using multiple SDSS
photometric observations (at least four per band, with a median of 10)
in the ugriz system. The catalog includes 1.01 million nonvariable
unresolved objects from the equatorial stripe 82
(|δJ2000.0|<1.266°) in the right ascension range
20h34m-4h00m and with the corresponding r-band (approximately
Johnson V-band) magnitudes in the range 14-22. The distributions of
measurements for individual sources demonstrate that the photometric
pipeline correctly estimates random photometric errors, which are
below 0.01mag for stars brighter than 19.5, 20.5, 20.5, 20, and 18.5
in ugriz, respectively (about twice as good as for individual SDSS
runs). Several independent tests of the internal consistency suggest
that the spatial variation of photometric zero points is not larger
than ∼0.01mag (rms). In addition to being the largest available data
set with optical photometry internally consistent at the ∼1% level,
this catalog provides a practical definition of the SDSS photometric
system. Using this catalog, we show that photometric zero points for
SDSS observing runs can be calibrated within a nominal uncertainty of
2% even for data obtained through 1mag thick clouds, and we
demonstrate the existence of He and H white dwarf sequences using
photometric data alone. Based on the properties of this catalog, we
conclude that upcoming large-scale optical surveys such as the Large
Synoptic Survey Telescope will be capable of delivering robust 1%
photometry for billions of sources.
Description:
A quick selection summary for the SDSS Stripe 82 standard star
catalog:
1) unresolved source in imaging data, at least one band with
photometric error below 0.05mag
2) processing flags BRIGHT, SATUR, BLENDED, or EDGE are not set
3) at least 4 observations in gri
4) non-variable (chi2<3 in gri)
5) the final standard error of the mean r band mag: <0.05mag
The random photometric errors are below 0.01mag for stars brighter
than (19.5, 20.5, 20.5, 20, 18.5) in ugriz, respectively (about twice
as good as for individual SDSS runs). The spatial variation of
photometric zeropoints is not larger than 0.01mag (rms).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stdcat.dat 250 1006849 *SDSS Stripe 82 Standard Star Catalog (v2.6)
varcat.dat 136 67507 Master SDSS Stripe 82 Variable Source Catalog (v1.1)
lcs/* . 67508 *Light curves in ASCII format for each variable source
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Note on stdcat.dat: IMPORTANT:
1) To select sources with reliable photometry in the u and z bands, don't
forget to require Nobs≥4
2) To avoid a slight bias (∼0.02mag) at the faint end in the gri bands,
require e_mag*sqrt(Nobs)<0.03
Note on lcs/*: Each source has its light curves listed separately, in file
named "LC_ID.dat", where ID comes from the master catalog. These files list
MJD (not sorted), band (ugriz), magnitude (uncorrected for ISM extinction)
and its error. Unreliable measurements are commented out (lines starting
with #; they were not removed to signify that an image/observation does
exist).
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
V/141 : Light-Motion Curve Catalogue (LMCC) in Stripe 82 (Bramich+ 2008)
J/ApJ/798/122 : Abundances from SEGUE (Miller+, 2015)
J/ApJS/210/22 : Herschel Stripe 82 survey (HerS) first cat. (Viero+, 2014)
J/MNRAS/441/1802 : Low-redshift QSOs in SDSS Stripe 82 (Karhunen+, 2014)
J/MNRAS/439/1212 : Deep 20GHz survey of CDFS & SDSS Stripe 82 (Franzen+, 2014)
J/MNRAS/436/3581 : X-ray observations of Stripe 82 (LaMassa+, 2013)
J/ApJ/731/17 : Low-mass star variability in SDSS Stripe 82 (Becker+, 2011)
J/A+A/525/A37 : QSO variability indexes in SDSS Stripe 82 (Meusinger+, 2011)
J/ApJS/186/233 : Variable point sources in SDSS stripe 82. I. (Bhatti+, 2010)
J/AJ/131/1184 : Recalibration of optical photometry (Maiz-Apellaniz+, 2006)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: stdcat.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- --- [CALIBSTARS]
12- 22 F11.7 deg RAdeg Right ascension in decimal degrees (J2000)
24- 34 F11.7 deg DEdeg Declination in decimal degrees (J2000)
36- 41 F6.4 arcsec e_RAdeg [0/0.5] Right ascension rms (1)
43- 48 F6.4 arcsec e_DEdeg [0/0.8] Declination rms (1)
50- 52 I3 --- Nep [4/29] Total number of epochs
54- 59 F6.3 mag Ar [0.03/1.7] ISM extinction value in the r band (2)
61- 63 I3 --- Nu [0/28] Total number of observations in u band
65- 70 F6.3 mag umed [-0.4/27.6] Median u magnitude
72- 77 F6.3 mag umag [-0.4/27.9] Mean u-band magnitude
79- 84 F6.3 mag e_umag [0/0.3] Standard error on umag (3)
86- 91 F6.3 mag s_umag [0/4] u-band root-mean-square scatter
93- 97 F5.1 --- uchi2 [0/442] chi2 per degree of freedom (computed
using the mean u-band magnitude)
99-101 I3 --- Ng [4/28] Total number of observations in g band
103-108 F6.3 mag gmed [13.76/23.78] Median g magnitude
110-115 F6.3 mag gmag [13.76/23.73] Mean g-band magnitude
117-122 F6.3 mag e_gmag [0.002/0.2] Standard error on gmag (3)
124-129 F6.3 mag s_gmag [0/0.5] g-band root-mean-square scatter
131-135 F5.1 --- gchi2 [0/3] chi2 per degree of freedom (computed using
the mean g-band magnitude)
137-139 I3 --- Nr [4/28] Total number of observations in r band
141-146 F6.3 mag rmed [13.4/21.9] Median r magnitude
148-153 F6.3 mag rmag [13.4/21.87] Mean r-band magnitude
155-160 F6.3 mag e_rmag [0.002/0.05] Standard error on rmag (3)
162-167 F6.3 mag s_rmag [0/0.4] r-band root-mean-square scatter
169-173 F5.1 --- rchi2 [0/3] chi2 per degree of freedom (computed using
the mean r-band magnitude)
175-177 I3 --- Ni [4/28] Total number of observations in i band
179-184 F6.3 mag imed [13.27/22.18] Median i magnitude
186-191 F6.3 mag imag [13.27/22.15] Mean i-band magnitude
193-198 F6.3 mag e_imag [0.002/0.2] Standard error on imag (3)
200-205 F6.3 mag s_imag [0.001/0.5] i-band root-mean-square scatter
207-211 F5.1 --- ichi2 [0/3] chi2 per degree of freedom (computed using
the mean i-band magnitude)
213-215 I3 --- Nz [0/28] Total number of observations in z band
217-222 F6.3 mag zmed [-0.03/21.8] Median z magnitude
224-229 F6.3 mag zmag [-0.03/21.9] Mean z-band magnitude
231-236 F6.3 mag e_zmag [0/0.3] Standard error on zmag (3)
238-243 F6.3 mag s_zmag [0/1.2] z-band root-mean-square scatter
245-250 F6.1 --- zchi2 [0/2088] chi2 per degree of freedom (computed
using the mean z-band magnitude)
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Note (1): Standard errors can be computed as rms/sqrt(Ntot).
Note (2): The Schlegel, Finkbeiner & Davis (1998ApJ...500..525S 1998ApJ...500..525S) extinction
value in the r band; extinction in other bands can be computed as
[Rv=3.1]: Am=Cm*Ar, with Cm=(1.873, 1.377, 0.758, 0.537) for m=(ugiz).
Note (3): 1.25 larger for the median
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Byte-by-byte Description of file: varcat.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID [74/7913299] Identifier (used for light curves
identification)
11- 20 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
25- 33 F9.6 deg DEdeg Declination in decimal degrees (J2000)
37- 50 F14.8 d Per [0.2/17518.1] Period (1)
53- 57 F5.2 mag rmag [12.6/21.2] SDSS r band magnitude (2)
59- 64 F6.2 mag u-g [-30.3/7.8] SDSS (u-g) color index (2)
67- 71 F5.2 mag g-r [-1.3/3.22] SDSS (g-r) color index (2)
74- 78 F5.2 mag r-i [-2.6/29.2] SDSS (r-i) color index (2)
80- 85 F6.2 mag i-z [-29/30] SDSS (i-z) color index (2)
88- 90 I3 --- Ng [10/145] Number of data points in the g band
93- 97 F5.3 mag gAmp [0.01/8] Amplitude (max-min) in the g band
100-102 I3 --- Nr [10/152] Number of data points in the r band
105-109 F5.3 mag rAmp [0.01/5.8] Amplitude (max-min) in the r band
112-114 I3 --- Ni [0/154] Number of data points in the i band
116-121 F6.3 mag iAmp [-2.1/8.7] Amplitude (max-min) in the i band (3)
123-128 F6.3 --- zQSO [0.08/4.1]?=-9.9 Redshift if spectroscopically
confirmed SDSS quasar
130-136 F7.3 mag iMag [-29.4/-22]?=-9.9 Absolute magnitude in
the i band if quasar
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Note (1): Period determined as the most likely period returned by MACHO's
Supersmoother algorithm (of course, there is no guarantee that a source
is truly periodic, or that this period is not aliased - be very careful
and look at phased light curves).
Note (2): Corrected for ISM extinction using SFD maps.
Impossible values (>20mag or ←10mag) should be ignored.
Note (3): Non-positive amplitudes correspond all to less than 5 observations
in the i-band, and should be ignored (Zeljko Ivezic, private communication);
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History:
Candidate standard stars catalog downloaded from:
http://www.astro.washington.edu/users/ivezic/sdss/catalogs/stripe82.html
Candidate variable sources catalog and LCs downloaded from:
http://www.astro.washington.edu/users/ivezic/sdss/catalogs/S82variables.html
(End) Emmanuelle Perret [CDS] 08-Jul-2015