J/AJ/146/87 AGN photometry. II. A catalog from the CFHTLS (Dong+, 2013)
Detecting active galactic nuclei using multi-filter imaging data.
II. Incorporating artificial neural networks.
Dong X.Y., De Robertis M.M.
<Astron. J., 146, 87 (2013)>
=2013AJ....146...87D 2013AJ....146...87D
ADC_Keywords: Galaxy catalogs ; Active gal. nuclei ; Redshifts ;
Photometry, ugriz ; Morphology
Keywords: galaxies: active - galaxies: photometry - methods: data analysis -
methods: statistical - techniques: image processing
Abstract:
This is the second paper of the series Detecting Active Galactic
Nuclei Using Multi-filter Imaging Data. In this paper we review
shapelets, an image manipulation algorithm, which we employ to adjust
the point-spread function (PSF) of galaxy images. This technique is
used to ensure the image in each filter has the same and sharpest PSF,
which is the preferred condition for detecting AGNs using multi-filter
imaging data as we demonstrated in Paper I of this series. We apply
shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey
ugriz images. Photometric parameters such as effective radii,
integrated fluxes within certain radii, and color gradients are
measured on the shapelets-reconstructed images. These parameters are
used by artificial neural networks (ANNs) which yield: photometric
redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy
morphological types with an uncertainty less than 2 T types for
z≤0.1; and identification of galaxies as AGNs with 70% confidence,
star-forming/starburst (SF/SB) galaxies with 90% confidence, and
passive galaxies with 70% confidence for z≤0.1. The incorporation of
ANNs provides a more reliable technique for identifying AGN or SF/SB
candidates, which could be very useful for large-scale multi-filter
optical surveys that also include a modest set of spectroscopic data
sufficient to train neural networks.
Description:
The primary data used for this study are from the Canada-France-Hawaii
Telescope Legacy Survey (cFHTLS), a survey carried out with the CFHT
3.6m telescope between 2003 and 2009. Data we used are from CFHTLS
data release 5, T0005, which contains 19 out of 25 W4 fields and data
release 6, T0006 (http://terapix.iap.fr/cplt/T0006-doc.pdf), which
contains the remaining 6 fields of W4. The secondary data are from the
SDSS DR7 main galaxy catalog.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 90 2515 The catalog of results
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See also:
II/317 : The CFHTLS Survey (T0007 release) (Hudelot+ 2012)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJS/186/427 : Detailed morphology of SDSS galaxies (Nair+, 2010)
J/A+A/461/81 : Galaxy clusters in the CFHTLS (Olsen+, 2007)
J/AJ/134/579 : SDSS DR3 morphologically classified galaxies (Fukugita+, 2007)
J/AJ/128/163 : Galaxy morphological classification (Lotz+, 2004)
http://terapix.iap.fr/cplt/T0006-doc.pdf : The CFHTLS T0006 release
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [W4]
3- 6 A4 --- W4 CFHTLS W4 sub-field designation (1)
8- 13 I6 --- Galaxy [3/256725] Object identifier in CFHTLS field (1)
15- 25 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
27- 36 F10.7 deg DEdeg Declination in decimal degrees (J2000)
38- 43 F6.3 --- z [-0.033/0.1] Redshift
45 I1 --- r_z [1/2] type; 1=spectroscopic, 2=photometric (2)
47- 48 I2 --- TT Morphological type (3)
50 I1 --- r_TT [0/4] Origin of MType (4)
52- 58 A7 --- Class Galaxy spectral class (AGN, SF/SB, passive) (5)
60 I1 --- r_Class [1/4] Galaxy classification (6)
62- 66 F5.1 mag uMag [-45.4/-9] Absolute u band magnitude (7)
68- 72 F5.1 mag gMag [-96.7/-10] Absolute g band magnitude (7)
74- 78 F5.1 mag rMag [-24.1/198] Absolute r band magnitude (7)
80- 84 F5.1 mag iMag [-24.5/-9] Absolute i band magnitude (7)
86- 90 F5.1 mag zMag [-56.4/-10.7] Absolute z band magnitude (7)
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Note (1): CFHTLS = Canada-France-Hawaii Telescope Legacy Survey (T0007 release,
Hudelot et al., 2012, cat. II/317).
Note (2): Source of redshift:
1 = spectroscopic redshift from SDSS DR7 (cat. II/294);
2 = photometric redshift estimated by an Artificial Neural Network (ANN).
Note (3): Nair & Abraham (2010, cat. J/ApJS/186/427) classification scheme is:
-5 = c0, E0, E+;
-3 = S0-;
-2 = S0, S0+;
0 = S0/a;
1 = Sa;
2 = Sab;
3 = Sb;
4 = Sbc;
5 = Sc;
6 = Scd;
7 = Sd;
8 = Sdm;
9 = Sm;
10 = Im.
Note (4): Source of morphological type:
0 = from Nair & Abraham (2010, cat. J/ApJS/186/427);
1 = estimated by neural net MorphNet1;
2 = estimated by neural net MorphNet2;
4 = not explained in the text.
Note (5): Spectral classes are:
SF/SB = star-forming/starburst galaxy;
AGN = Active Galactic Nuclei.
Note (6): Origin of the classification:
1 = classified by MPA/JHU DR7 (Tremonti et al., 2004ApJ...613..898T 2004ApJ...613..898T);
2 = classified by MPA/JHU DR7 as "GALAXY", reclassified by emission-line ratios
3 = classified by neural net SpecNet1 as starburst or starforming galaxies;
4 = classified by neural net SpecNet1 and SpecNet2 as AGN or passive galaxies.
Note (7): After K-correction and Galactic extinction correction.
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History:
From electronic version of the journal
References:
Dong & De Robertis, Paper I, 2013
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 11-Jul-2014