J/ApJ/856/68 COSMOS lens candidates with LensFlow (Pourrahmani+, 2018)
LensFlow: a convolutional neural network in search of strong gravitational
lenses.
Pourrahmani M., Nayyeri H., Cooray A.
<Astrophys. J., 856, 68 (2018)>
=2018ApJ...856...68P 2018ApJ...856...68P
ADC_Keywords: Gravitational lensing; Photometry, HST; Optical
Keywords: gravitational lensing: strong ; methods: data analysis ;
techniques: image processing
Abstract:
In this work, we present our machine learning classification algorithm
for identifying strong gravitational lenses from wide-area surveys
using convolutional neural networks; LensFlow. We train and test the
algorithm using a wide variety of strong gravitational lens
configurations from simulations of lensing events. Images are
processed through multiple convolutional layers that extract feature
maps necessary to assign a lens probability to each image. LensFlow
provides a ranking scheme for all sources that could be used to
identify potential gravitational lens candidates by significantly
reducing the number of images that have to be visually inspected. We
apply our algorithm to the HST/ACS i-band observations of the COSMOS
field and present our sample of identified lensing candidates. The
developed machine learning algorithm is more computationally efficient
and complimentary to classical lens identification algorithms and is
ideal for discovering such events across wide areas from current and
future surveys such as LSST and WFIRST.
Description:
We used HST/ACS i-band observations in the full COSMOS field to search
for candidate gravitationally lensed sources.
LensFlow was able to identify 92 lenses in the COSMOS field, 46 of
which were new and the rest were previously reported in Faure+ (2008,
J/ApJS/176/19).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 46 92 Catalog of identified lenses by LensFlow
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See also:
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
J/ApJ/621/53 : Multiple arc systems in A1689 (Broadhurst+, 2005)
J/ApJS/176/19 : COSMOS: strong lens systems (Faure+, 2008)
J/ApJ/749/38 : CFHTLS-SL2S-ARCS strong lens candidates (More+, 2012)
J/ApJS/199/25 : CLASH sources for MACS1149.6+2223 (Postman+, 2012)
J/ApJ/797/138 : Properties of SMG lens candidates (Calanog+, 2014)
J/ApJ/785/144 : SL2S galaxy-scale sample of lens candidates (Gavazzi+, 2014)
J/ApJ/800/18 : HST/WFC3 observations of z∼7-8 galaxies in A2744 (Atek+, 2015)
J/ApJ/812/114 : Grism Lens-Amplified Survey from Space (GLASS) I. (Treu+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/92] Lens number (1)
4 A1 --- f_Seq [b] Flag on Seq (2)
7- 17 F11.6 deg RAdeg [149.4/150.8] Right ascension in
decimal degrees (J2000)
19- 27 F9.6 deg DEdeg [1.6/2.9] Declination in decimal degrees (J2000)
29- 32 F4.2 arcsec RE [0.3/3] Einstein radius
34- 38 F5.2 mag imag [18.5/23.6] HST/ACS i-band AB magnitude
40- 44 I5 --- Rank [1/13610] LensFlow absolute rank of the lens
among 236000 images
46- 46 A1 --- Grade [A-C] Average grade (3)
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Note (1): The numbers correspond to the image numbers in Figure 10.
Note (2):
b = These marked lenses were previously cataloged by
Faure+ (2008, J/ApJS/176/19 ; <[FKC2008] COSMOS MMSS+MMSS> in Simbad).
Note (3): Grade as follows:
A = images that are clearly a strong gravitational lens.
B = lenses correspond to images that are most likely a lens, but there is
a chance they could also be artifacts, noise, structures in elliptical
galaxies, satellite galaxies, tidally interacting galaxies, etc.
C = lenses consist of images that are most likely not a lens, but there is
a chance they might be gravitationally lensed.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 13-Feb-2019