When Spectral Modeling Meets Convolutional Networks: A Method for Discovering Reionization-era Lensed Quasars in Multiband Imaging Data
The Astrophysical Journal, vol. 943, pp. 150
Abstract
Abstract Over the last two decades, around 300 quasars have been discovered at z ≳ 6, yet only one has been identified as being strongly gravitationally lensed. We explore a new approach—enlarging the permitted spectral parameter space, while introducing a new spatial geometry veto criterion—which is implemented via image-based deep learning. We first apply this approach to a systematic search for reionization-era lensed quasars, using data from the Dark Energy Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, and the Wide-field Infrared Survey Explorer. Our search method consists of two main parts: (i) the preselection of the candidates, based on their spectral energy distributions (SEDs), using catalog-level photometry; and (ii) relative probability calculations of the candidates being a lens or some contaminant, utilizing a convolutional neural network (CNN) classification. The training data sets are constructed by painting deflected point-source lights over actual galaxy images, to generate realistic galaxy–quasar lens models, optimized to find systems with small image separations, i.e., Einstein radii of θ E ≤ 1″. Visual inspection is then performed for sources with CNN scores of P lens > 0.1, which leads us to obtain 36 newly selected lens candidates, which are awaiting spectroscopic confirmation. These findings show that automated SED modeling and deep learning pipelines, supported by modest human input, are a promising route for detecting strong lenses from large catalogs, which can overcome the veto limitations of primarily dropout-based SED selection approaches.
Authors 11
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I.T Andika corresponding
Ghent University · Max Planck Institute for Astronomy · Technical University of Munich
Affiliation as printed
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Physik-Department, Technische Universität München, James-Franck-Str. 1, D-85748 Garching, Germany
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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Affiliation as printed
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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Massachusetts Institute of Technology
Affiliation as printed
MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Ave., Cambridge, MA 02139, USA
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Bandung Institute of Technology
Affiliation as printed
Astronomy Research Group and Bosscha Observatory, FMIPA, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia
U-CoE AI-VLB, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia
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Affiliation as printed
Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, 8320000, Chile
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Kavli Institute for the Physics and Mathematics of the Universe · Peking University · The University of Tokyo
Affiliation as printed
Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, People's Republic of China
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, Chiba 277-8583, Japan
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Leiden University · Max Planck Institute for Astronomy · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; irham.andika@tum.de
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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