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Geometric Corroboration of the Earliest Lensed Galaxy at z ≃ 10.8 from Robust Free-form Modelling

Chan, Brian M. Y. and Broadhurst, Tom and Lim, Jeremy and Diego, Jose M. and Zitrin, Adi and Coe, Dan and Ford, Holland C. (2017) Geometric Corroboration of the Earliest Lensed Galaxy at z ≃ 10.8 from Robust Free-form Modelling. Astrophysical Journal, 835 (1). Art. No. 44. ISSN 0004-637X. doi:10.3847/1538-4357/835/1/44.

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A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of z ≃ 10.7_(-0.4)^(+0.6) is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent-lensing-based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at z = 0.591). Our lens model uses the nine sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey toward this cluster. We convincingly exclude the low-redshift regime of z < 3, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of z≃ 10.8_(-0.4)^(+0.3) for MACS0647-JD, strongly supporting the higher photometric redshift solution. Importantly, we find a tight linear relation between the relative brightnesses of all nine sets of multiply lensed images and their relative magnifications as predicted by our model. This agreement provides a benchmark for the quality of the lens model, and establishes the robustness of our free-form lensing method for measuring model-independent geometric source distances and for deriving objective central cluster mass distributions. After correcting for its magnification the luminosity of MACS0647-JD remains relatively high at M UV = −19.4, which is within a factor of a few in flux of some surprisingly luminous z sime 10–11 candidates discovered recently in Hubble blank field surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Diego, Jose M.0000-0001-9065-3926
Zitrin, Adi0000-0002-0350-4488
Coe, Dan0000-0001-7410-7669
Additional Information:© 2017. The American Astronomical Society. Received 2016 September 15. Accepted 2016 November 16. Published 2017 January 17. The work is based on observations made with the NASA/ESA Hubble Space Telescope and operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. T.J.B. gratefully acknowledges the Visiting Research Professor Scheme at the University of Hong Kong. J.M.D. acknowledges support of the consolider project AYA2015-64508-P (MINECO/FEDER, UE), CAD2010-00064 and AYA2012-39475-C02-01 funded by the Ministerio de Economia y Competitividad, and support from the Department of Physics at The University of Hong Kong for a visit to work on this project. J.L. acknowledges support from the University of Hong Kong via a Seed Funding Program for Basic Research through grant 201411159166 at the start of this project, thus enabling follow-up support from the Research Grants Council of Hong Kong through grant 17319316.
Funding AgencyGrant Number
NASANAS 5-26555
Ministerio de Economia y Competitividad (MINECO)/FEDER/UEAYA2015-64508-P
Ministerio de Economia y Competitividad (MINECO)/FEDER/UECAD2010-00064
Ministerio de Economia y Competitividad (MINECO)AYA2012-39475-C02-01
University of Hong Kong20141115916
Hong Kong Research Grants Council17319316
Subject Keywords:dark matter; galaxies: high-redshift; gravitational lensing: strong
Issue or Number:1
Record Number:CaltechAUTHORS:20170120-092325772
Persistent URL:
Official Citation:Brian M. Y. Chan et al 2017 ApJ 835 44
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73568
Deposited By: Ruth Sustaita
Deposited On:22 Jan 2017 17:14
Last Modified:11 Nov 2021 05:18

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