J/A+A/584/A44 Photometric classification of QSO from RCS-2 (Carrasco+, 2015)
Photometric Classification of quasars from RCS-2 using Random Forest.
Carrasco D., Barrientos L.F., Pichara K., Anguita T., Murphy D.N.A.,
Gilbank D.G., Gladders M.D., Yee H.K.C., Hsieh B.C., Lopez S.
<Astron. Astrophys. 584, A44 (2015)>
=2015A&A...584A..44C 2015A&A...584A..44C (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Photometry, SDSS ; Photometry, ultraviolet
Keywords: techniques: photometric - quasars: general - surveys - catalogs
Abstract:
We present new quasar candidate catalogs from the Red-Sequence Cluster
Survey 2 (RCS-2), identified solely from photometric information using
a Random Forest algorithm. The algorithm is trained using a
well-defined SDSS spectroscopic sample of quasars and stars. The
algorithm identifies putative quasars from broadband magnitudes (g, r,
i, z) and colors. Exploiting NUV GALEX measurements for a subset of
the objects, we refine the classifier by adding new information. An
additional subset of the data with WISE W1 and W2 bands is also
studied. Upon analyzing 542,897 RCS-2 point sources, the algorithm
identified 21,501 quasar candidates, with a training-set-derived
precision of 89.5% and recall of 88.4%. These performance metrics
improve for the GALEX subset; 6530 quasar candidates are identified
from 16898 sources, with a precision and recall respectively of 97.0%
and 97.5%. Algorithm performance is further improved when WISE data
are included, with precision and recall increasing to 99.3% and 99.1%
respectively for 21834 quasar candidates from 242902 sources. After
merging these samples and removing duplicates, we obtain 38257
candidates.
Description:
The catalogs contain the quasar candidates with their coordinates,
magnitudes, respective errors, and an indicator of whether or not they
were classified as quasars in the other two samples.
We present three separate catalogs. Table1 corresponds to the
candidates selected from DS1, matching the training set magnitude
distribution and using only RCS-2 photometric information. Table2
contains the candidates from DS2, where objects with detection in the
NUV GALEX band were used. Table3 includes the candidates from DS3,
where information from W1 and W2 bands from WISE was used.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 21501 Quasar candidates from DS1
table2.dat 89 6529 Quasar candidates from DS2
table3.dat 102 21834 Quasar candidates from DS3
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See also:
J/ApJS/157/1 : Red-Sequence Cluster Survey (Gladders+, 2005)
J/ApJS/158/161 : Photometric redshift catalog from the RCS (Hsieh+, 2005)
J/ApJ/749/150 : Group galaxies in the RCS (Li+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 h RAhour Right ascension in decimal hours (J2000)
11- 20 F10.6 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag gmag AB magnitude in the g band from RCS-2
29- 33 F5.3 mag e_gmag Photometric error in the g band from RCS-2
35- 40 F6.3 mag rmag AB magnitude in the r band from RCS-2
42- 46 F5.3 mag e_rmag Photometric error in the r band from RCS-2
48- 53 F6.3 mag imag AB magnitude in the i band from RCS-2
55- 59 F5.3 mag e_imag Photometric error in the i band from RCS-2
61- 66 F6.3 mag zmag AB magnitude in the z band from RCS-2
68- 72 F5.3 mag e_zmag Photometric error in the z band from RCS-2
74 I1 --- DS2 [0/1] Whether the object is classified as a
quasar from DS2 (1: true)
76 I1 --- DS3 [0/1] Whether the object is classified as a
quasar from DS3 (1: true)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 h RAhour Right Ascension in decimal hours (J2000)
11- 20 F10.6 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag NUV AB magnitude in the NUV band from GALEX
29- 33 F5.3 mag e_NUV Photometric error in the NUV band from GALEX
35- 40 F6.3 mag gmag AB magnitude in the g band from RCS-2
42- 46 F5.3 mag e_gmag Photometric error in the g band from RCS-2
48- 53 F6.3 mag rmag AB magnitude in the r band from RCS-2
55- 59 F5.3 mag e_rmag Photometric error in the r band from RCS-2
61- 66 F6.3 mag imag AB magnitude in the i band from RCS-2
68- 72 F5.3 mag e_imag Photometric error in the i band from RCS-2
74- 79 F6.3 mag zmag AB magnitude in the z band from RCS-2
81- 85 F5.3 mag e_zmag Photometric error in the z band from RCS-2
87 I1 --- DS1 [0/1] Whether the object is classified as a
quasar from DS1 (1: true)
89 I1 --- DS3 [0/1] Whether the object is classified as a
quasar from DS3 (1: true)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 h RAhour Right Ascension in decimal hours (J2000)
11- 20 F10.6 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag gmag AB magnitude in the g band from RCS-2
29- 33 F5.3 mag e_gmag Photometric error in the g band from RCS-2
35- 40 F6.3 mag rmag AB magnitude in the r band from RCS-2
42- 46 F5.3 mag e_rmag Photometric error in the r band from RCS-2
48- 53 F6.3 mag imag AB magnitude in the i band from RCS-2
55- 59 F5.3 mag e_imag Photometric error in the i band from RCS-2
61- 66 F6.3 mag zmag AB magnitude in the z band from RCS-2
68- 72 F5.3 mag e_zmag Photometric error in the z band from RCS-2
74- 79 F6.3 mag W1mag AB magnitude in the W1 band from WISE
81- 85 F5.3 mag e_W1mag Photometric error in the W1 band from WISE
87- 92 F6.3 mag W2mag AB magnitude in the W2 band from WISE
94- 98 F5.3 mag e_W2mag Photometric error in the W2 band from WISE
100 I1 --- DS1 [0/1] Whether the object is classified as a
quasar from DS1 (1: true)
102 I1 --- DS2 [0/1] Whether the object is classified as a
quasar from DS2 (1: true)
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Acknowledgements:
Daniela Carrasco, dcarrasco(at)student.unimelb.edu.au
References:
Gilbank et al., 2011AJ....141...94G 2011AJ....141...94G : RCS-2 presentation
(End) D. Carrasco [Univ. of Melbourne, Australia], P. Vannier [CDS] 25-Aug-2015