J/ApJS/176/19 COSMOS: strong lens systems (Faure+, 2008)
First catalog of strong lens candidates in the COSMOS field.
Faure C., Kneib J.-P., Covone G., Tasca L., Leauthaud A., Capak P.,
Jahnke K., Smolcic V., De La Torre S., Ellis R., Finoguenov A.,
Koekemoer A., Le Fevre O., Massey R., Mellier Y., Refregier A., Rhodes J.,
Scoville N., Schinnerer E., Taylor J., Van Waerbeke L., Walcher J.
<Astrophys. J. Suppl. Ser., 176, 19-38 (2008)>
=2008ApJS..176...19F 2008ApJS..176...19F
ADC_Keywords: Models ; Gravitational lensing ; Photometry, HST ; Redshifts
Keywords: catalogs - galaxies: statistics - gravitational lensing
Abstract:
We present the first catalog of 67 strong galaxy-galaxy lens
candidates discovered in the 1.64deg2 Hubble Space Telescope COSMOS
survey. Twenty of these systems display multiple images or strongly
curved large arcs. Our initial search is performed by visual
inspection of the data and is restricted, for practical
considerations, to massive early-type lens galaxies with arcs found at
radii smaller than ∼5". Simple mass models are constructed for the
best lens candidates, and our results are compared to the strong
lensing catalogs of the SLACS survey and the CASTLES database. These
new strong galaxy-galaxy lensing systems constitute a valuable sample
to study the mass distribution of early-type galaxies and their
associated dark matter halos.
Description:
Three key data sets of the COSMOS survey were used: the HST ACS
high-resolution imaging, the Subaru Suprime imaging, and the CFHT
Megacam multicolor imaging.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 93 20 Summary of the lensing galaxy parameters for the
best systems
table2.dat 93 47 Summary of the lensing galaxy parameters for the
single arclet systems
table4.dat 64 16 Morphological parameters and Einstein radii of
the lensing galaxies for the best systems
pcat.dat 201 9452 Photometric redshift catalog selected from
Capak et al. (2007, Cat. II/284)
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See also:
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
J/ApJ/600/L155 : Gravitational lens in GOODS ACS fields (Fassnacht+, 2004)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- COSMOS Lens candidate name (MMSS+MMSS)
10 A1 --- f_COSMOS [f] indicate that the object was found
fortuitously
12- 13 I2 h RAh Hour of right ascension (J2000)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 21 F4.1 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of declination (J2000)
33- 36 F4.2 --- zph ?=- Photometric redshift of the lens
38- 41 F4.2 --- E_zph ? Positive error on redshift (68%
confidence level)
43- 46 F4.2 --- e_zph ? Negative error on redshift (68%
confidence level)
48- 52 F5.2 arcsec r Largest radius of the arc
54- 57 F4.2 arcsec reff ?=- Effective radius of the lensing galaxy
from the surface brightness fitting
59- 61 F3.1 --- n ?=- Sersic profile index
63- 67 F5.2 mag F814W ?=- Total magnitude of the lensing galaxy
in the WFPC/F814W band
69- 72 F4.2 mag E_F814W ? Positive error on total magnitude
74- 77 F4.2 mag e_F814W ? Negative error on total magnitude
79- 83 F5.1 deg PA [-90/90]? Lensing galaxy position angle
85- 88 F4.2 --- Ell ?=- Galaxy ellipticity
90- 93 F4.1 mag/arcsec2 sb814W ?=- Magnitude of the brightest image in
the WFPC/F814W band in mag/arcsec2
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- COSMOS Name (MMSS+MMSS)
11- 14 F4.2 --- zl Lens redshift used for the modeling
16- 19 F4.2 --- zs Source redshift used for the modeling
21- 25 F5.2 --- chi2 ?=- χ2 of the fit between the best mass
model and the data
27- 31 F5.1 km/s sigV Velocity dispersion of the lens
33- 36 F4.2 arcsec Erad Einstein radius of the lens
38- 41 F4.2 --- gamma ?=- Value of the shear (2)
43- 47 F5.1 deg theta ?=- Orientation of the shear (2)
49- 57 A9 --- Images Yes if more images appear during the modeling
("no" otherwise) (1)
59- 64 A6 --- Mult Multiplicity of the images used for the mass
modeling
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Note (1): Comments in brackets following "yes" or "no" mean:
1 = The mass model is created using a source aligned with the lens center,
and we scale σv in order to match the ring size.
2 = The angular distance between the images and the velocity dispersion of
the lens makes us think that the lensing galaxy is associated with a
galaxy group or cluster.
3 = The χ2 value is high, suggesting that this system is not a
genuine lens, or that a simple mass model is not a good representation
of the total lens potential.
Note (2): an external shear contribution is added when the Singular
Isothermal Ellipsoid (SIE) alone cannot reproduce the image configuration.
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Byte-by-byte Description of file: pcat.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_Seq [*] * for possible strong galaxy-galaxy
lens system
3- 8 I6 --- Seq Sequential number
10 I1 --- SpType [1] Spectral type
12- 22 F11.7 deg RAdeg Right ascension in decimal degrees (J2000)
24- 32 F9.7 deg DEdeg Declination in decimal degrees (J2000)
34- 39 F6.4 --- zph ?=9.9999 Photometric redshift
41- 44 F4.2 --- zph.l Lower limit of photometric redshift
45- 46 A2 --- --- [00]
48- 51 F4.2 --- zph.u Upper limit of photometric redshift
52- 53 A2 --- --- [00]
55- 66 E12.7 --- chi2.1 Chi2 value (undefined)
68- 79 E12.7 --- chi2.2 Chi2 value (undefined)
81- 87 F7.3 mag u*MAG ?=-99.990 Absolute CFHT u* magnitude
89- 95 F7.3 mag BjMAG ?=-99.990 Absolute Subaru Bj magnitude
97-103 F7.3 mag VjMAG ?=-99.990 Absolute Subaru Vj magnitude
105-111 F7.3 mag g+MAG ?=-99.990 Absolute Subaru g+ magnitude
113-119 F7.3 mag r+MAG ?=-99.990 Absolute Subaru r+ magnitude
121-127 F7.3 mag i+MAG ?=-99.990 Absolute Subaru i+ magnitude
129-135 F7.3 mag z+MAG ?=-99.990 Absolute Subaru z+ magnitude
137-143 F7.3 mag KMAG ?=-99.990 Absolute CTIO/KPNO Ks magnitude
145-151 F7.3 mag i*MAG ?=-99.990 Absolute CFHT i* magnitude
153-159 F7.3 mag uMAG ?=-99.990 Absolute SDSS u magnitude
161-167 F7.3 mag gMAG ?=-99.990 Absolute SDSS g magnitude
169-175 F7.3 mag rMAG ?=-99.990 Absolute SDSS r magnitude
177-183 F7.3 mag iMAG ?=-99.990 Absolute SDSS i magnitude
185-191 F7.3 mag zMAG ?=-99.990 Absolute SDSS z magnitude
193-199 F7.3 mag F814MAG ?=-99.990 Absolute HST F814W magnitude
201 I1 --- Class [1] Star/galaxy classifier (1=galaxy)
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 08-Jul-2009