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Galaxy Ellipticity Measurements in the Near-infrared for Weak Lensing

Lee, Bomee and Chary, Ranga-Ram and Wright, Edward L. (2018) Galaxy Ellipticity Measurements in the Near-infrared for Weak Lensing. Astrophysical Journal, 866 (2). Art. No. 157. ISSN 1538-4357. doi:10.3847/1538-4357/aadfd7.

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We investigate the value of the near-infrared imaging from upcoming surveys for constraining the ellipticities of galaxies. We select galaxies between 0.5 ≤ z < 3 that are brighter than expected Euclid sensitivity limits from the GOODS-S and N fields in CANDELS. The co-added CANDELS/HST V+I and J+H images are degraded in resolution and sensitivity to simulate Euclid-quality optical and near-infrared (NIR) images. We then run GALFIT on these simulated images and find that optical and NIR provide similar performances in measuring galaxy ellipticities at redshifts 0.5 ≤ z < 3. At z > 1.0, the NIR-selected source density is higher by a factor of 1.4 and therefore the standard error in NIR-derived ellipticities is about 30% smaller, implying a more precise ellipticity measurement. The good performance of the NIR is mainly because galaxies have an intrinsically smoother light distribution in the NIR bands than in the optical, the latter tracing the clumpy star-forming regions. In addition, the NIR bands have a higher surface brightness per pixel than the optical images, while being less affected by dust attenuation. Despite the worse spatial sampling and resolution of Euclid NIR compared to optical, the NIR approach yields equivalent or more precise galaxy ellipticity measurements. If systematics that affect shape such as dithering strategy and point-spread function undersampling can be mitigated, inclusion of the NIR can improve galaxy ellipticity measurements over all redshifts. This is particularly important for upcoming weak lensing surveys, such as with Euclid and WFIRST.

Item Type:Article
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URLURL TypeDescription Paper
Lee, Bomee0000-0003-1954-5046
Chary, Ranga-Ram0000-0001-7583-0621
Wright, Edward L.0000-0001-5058-1593
Additional Information:© 2018 The American Astronomical Society. Received 2018 May 20; revised 2018 September 5; accepted 2018 September 5; published 2018 October 24. This work is partly funded by NASA/Euclid grant 1484822 and is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The authors thank the anonymous referee for very useful comments that helped to improve the presentation of the paper. We also thank Lance Miller, Stefanie Wachter, Peter Schneider, Henk Hoekstra, and Jason Rhodes for thoughtful comments that improved this manuscript.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:gravitational lensing: weak – cosmology: observations
Issue or Number:2
Record Number:CaltechAUTHORS:20181024-162228041
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Official Citation:Bomee Lee et al 2018 ApJ 866 15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90408
Deposited By: Tony Diaz
Deposited On:25 Oct 2018 16:59
Last Modified:16 Nov 2021 03:32

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