J/ApJ/909/27 Strong gravitational lenses in DESI Legacy Surveys (Huang+, 2021)
Discovering new strong gravitational lenses in the DESI Legacy Imaging Surveys.
Huang X., Storfer C., Gu A., Ravi V., Pilon A., Sheu W., Venguswamy R.,
Banka S., Dey A., Landriau M., Lang D., Meisner A., Moustakas J.,
Myers A.D., Sajith R., Schlafly E.F., Schlegel D.J.
<Astrophys. J., 909, 27 (2021)>
=2021ApJ...909...27H 2021ApJ...909...27H
ADC_Keywords: Gravitational lensing; Surveys; Redshifts; Photometry, ugriz
Keywords: Strong gravitational lensing ; High-redshift galaxies ;
AGN host galaxies ; Galaxies ; Galaxy clusters ; Galaxy groups ;
Quasars
Abstract:
We have conducted a search for new strong gravitational lensing
systems in the Dark Energy Spectroscopic Instrument Legacy Imaging
Surveys' Data Release 8. We use deep residual neural networks,
building on previous work presented by Huang+ (2020 J/ApJ/894/78).
These surveys together cover approximately one-third of the sky
visible from the Northern Hemisphere, reaching a z-band AB magnitude
of ∼22.5. We compile a training sample that consists of known lensing
systems as well as non-lenses in the Legacy Surveys and the Dark
Energy Survey. After applying our trained neural networks to the
survey data, we visually inspect and rank images with probabilities
above a threshold. Here we present 1210 new strong lens candidates.
Description:
The Legacy Imaging Surveys consist of three projects: the Dark Energy
Camera Legacy Survey (DECaLS), observed by the Dark Energy Camera
(DECam) on the 4m Blanco telescope at the Cerro Tololo Inter-American
Observatory; the Beijing-Arizona Sky Survey (BASS), by the 90Prime
camera on the Bok 2.3m telescope owned and operated by the University
of Arizona and located on Kitt Peak; and the Mayall z-band Legacy
Survey (MzLS), by the Mosaic3 camera on the 4m Mayall telescope at
Kitt Peak National Observatory. Together they cover ∼14000deg2 of
the extragalactic sky visible from the Northern Hemisphere with at
least three passes in each of the three bands, grz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cand.dat 105 1312 Gravitational lens candidates
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See also:
J/ApJ/682/964 : Sloan lens ACS survey. V. (Bolton+, 2008)
J/ApJ/834/210 : Sp. of strong lensing galaxy clusters (Carrasco+, 2017)
J/ApJS/232/15 : Candidate strong lens systems from DES obs. (Diehl+, 2017)
J/ApJ/851/48 : SLACS. XIII. Galaxy-scale strong lens cand. (Shu+, 2017)
J/ApJ/856/68 : COSMOS lens candidates with LensFlow (Pourrahmani+, 2018)
J/ApJ/867/107 : SuGOHI. II. Lenses from HSC SSP DR2 & env. (Wong+, 2018)
J/MNRAS/484/5330 : High-z strong lens candidates from DES (Jacobs+, 2019)
J/ApJS/243/17 : Strong DES lens cand. from neural networks (Jacobs+, 2019)
J/ApJ/876/85 : HST observations for LMC Cepheids (Riess+, 2019)
J/ApJ/894/78 : Strong gravitational lenses from DECaLS (Huang+, 2020)
http://www.legacysurvey.org/ : DESI Legacy Imaging Surveys home page
Byte-by-byte Description of file: cand.dat
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Bytes Format Units Label Explanations
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1 A1 --- Q [ABC] Grade of the lens candidate
(A=high level of confidence, 216 occurrences)
3- 6 I4 --- Seq [0/1311] Running sequence number
8- 11 I4 --- Img [1/1312] Cutout image number
13- 33 A21 --- Name Name of the system
(DESI-DDD.dddd+DD.dddd; J2000)
35- 37 A3 --- Type Tractor Type ("DC" or "REX"=round exponential
galaxy model) (1)
39- 41 F3.1 --- Score [2/4] Human inspection average score
43 I1 --- delSc [0/2] Score absolute difference
45- 48 F4.2 --- Prob [0.08/1] ResNet probability
50- 55 F6.4 --- zsp [0.1/0.9]? Spectroscopic redshift (SDSS DR16)
57- 61 F5.3 --- zph [0.07/1.03]? Photometric redshift
from Zhou+ 2021MNRAS.501.3309Z 2021MNRAS.501.3309Z
63- 67 F5.3 --- e_zph [0.005/0.4]? zph uncertainty
69- 76 A8 --- Mod ResNet Model ("L18" or "shielded") (2)
78- 80 A3 --- Ref [a-m, ] Reference(s) (3)
82- 86 F5.2 --- gmag [16.6/25.4] CTIO/DECam g-band magnitude
88- 92 F5.2 --- rmag [15.5/23.5] CTIO/DECam r-band magnitude
94- 98 F5.2 --- zmag [14.7/21.7] CTIO/DECam z-band magnitude
100-105 A6 --- Survey Region of the footprint ("DECaLS" or "MzLS")
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Note (1): The Legacy Surveys used The Tractor package (Lang et al. 2016,
Astrophysics Source Code Library ascl:1604.008) as a forward-modeling
approach to perform source extraction on pixel-level data. The Tractor
takes as input the individual images from multiple exposures in
multiple bands, with different seeing in each. After source detection,
the point source ("PSF") and spatially extended ("REX," round
exponential galaxy) models are computed for every source, and the
better of these two is used when deciding whether to keep the source.
The spatially extended sources (REX) are further classified according
to whether χ2 is improved by 9 by treating it as a de
Vaucouleurs (DEV) profile, an exponential (EXP) profile, or a
composite of DEV + EXP, or COMP. Here "DC" denotes DEV or COMP.
Note (2): The original model in L18=Lanusse+ 2018MNRAS.473.3895L 2018MNRAS.473.3895L or
the "shielded" model (the one with 32 output channels); see Section 3.3.
Note (3): Reference for the 102 known lenses or candidates. Code as follows:
a = Canameras et al. (2020, J/A+A/644/A163),
b = Carrasco et al. (2017, J/ApJ/834/210),
c = Inada et al. (2003AJ....126..666I 2003AJ....126..666I),
d = Jacobs et al. (2019, J/ApJS/243/17),
e = Jaelani et al. (2020MNRAS.495.1291J 2020MNRAS.495.1291J),
f = Lemon et al. (2020MNRAS.494.3491L 2020MNRAS.494.3491L),
g = Petrillo et al. (2019MNRAS.484.3879P 2019MNRAS.484.3879P),
h = Sharon et al. (2020, J/ApJS/247/12),
i = Shu et al. (2016, J/ApJ/824/86),
j = Sonnenfeld et al. (2013, J/ApJ/777/97),
k = Sonnenfeld et al. (2018PASJ...70S..29S 2018PASJ...70S..29S),
l = Sonnenfeld et al. (2020, J/A+A/642/A148).
m = Wong et al. (2018, J/ApJ/867/107);
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History:
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(End) Emmanuelle Perret [CDS] 05-Aug-2022