J/MNRAS/419/80 Photometric Classification Catalogue of SDSS DR7 (Abraham+, 2012)
A photometric catalogue of quasars and other point sources in the
Sloan Digital Sky Survey.
Abraham S., Philip N.S., Kembhavi A., Wadadekar Y.G., Sinha R.
<Mon. Not. R. Astron. Soc., 419, 80-94 (2012)>
=2012MNRAS.419...80A 2012MNRAS.419...80A
ADC_Keywords: Surveys ; QSOs ; Photometry, SDSS
Keywords: astronomical data bases: miscellaneous - catalogues -
techniques: photometric - methods: ststistical - surveys
Abstract:
We present a catalogue of about six million unresolved photometric
detections in the Sloan Digital Sky Survey (SDSS) Seventh Data
Release, classifying them into stars, galaxies and quasars. We use a
machine learning classifier trained on a subset of spectroscopically
confirmed objects from 14th to 22nd magnitude in the SDSS i band. Our
catalogue consists of 2430625 quasars, 3544036 stars and 63586
unresolved galaxies from 14th to 24th magnitude in the SDSS i-band.
Our algorithm recovers 99.96 per cent of spectroscopically confirmed
quasars and 99.51 per cent of stars to i∼21.3 in the colour window
that we study. The level of contamination due to data artefacts for
objects beyond i=21.3 is highly uncertain and all mention of
completeness and contamination in the paper are valid only for objects
brighter than this magnitude. However, a comparison of the predicted
number of quasars with the theoretical number counts shows reasonable
agreement.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 93 6038247 Photometric catalogue based on SDSS DR7
(a sample is published as Table 4)
table4.fit 2880 159347 FITS version of the catalogue
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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3- 20 A18 --- ObjID SDSS ObjID
22- 30 F9.5 deg RAdeg Right ascension in decimal degrees (J2000)
32- 40 F9.5 deg DEdeg Declination in decimal degrees (J2000)
42- 47 F6.3 mag umag SDSS u band PSF ubercalibrated asinh magnitude (1)
49- 54 F6.3 mag gmag SDSS g band PSF ubercalibrated asinh magnitude (1)
56- 61 F6.3 mag rmag SDSS r band PSF ubercalibrated asinh magnitude (1)
63- 68 F6.3 mag imag SDSS i band PSF ubercalibrated asinh magnitude (1)
70- 75 F6.3 mag zmag SDSS z band PSF ubercalibrated asinh magnitude (1)
78 I1 --- cl1 [1/6] Most probable class of the object (2)
80- 84 F5.1 % C1 Confidence the classifier has in the most
probable class
87 I1 --- cl2 [1/6] Second most probable class of the
object (2)
89- 93 F5.1 % C2 Confidence the classifier has in the second
most probable class
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Note (1): Magnitudes corrected from the galactic extinction.
The ubercalibrated magnitudes (Padmanabhan et al. 2008ApJ...674.1217P 2008ApJ...674.1217P)
represent the most robust photometric measurements as they are
calibrated across SDSS "stripes" to a single uniform photometric
system for the entire SDSS area.
Note (2): Class is numbered as follows:
1 = star
2 = galaxy
3 = low redshift Quasar
4 = high redshift Quasar
6 = late-star
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(End) Sheelu Abraham [IUCAA], Francois Ochsenbein [CDS] 26-Apr-2012