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A multiply-lensed galaxy, MACS0647-JD, with a probable photometric redshiftof $z\simeq 10.7^{+0.6}_{-0.4}$ is claimed to constitute one of the veryearliest known galaxies, formed well before reionization was completed.However, spectral evidence that MACS0647-JD lies at high redshift has proveninfeasible and so here we seek an independent lensing based "geometricredshift" derived from the angles between the three lensed images ofMACS0647-JD, using our free-form mass model (WSLAP+) for the lensing clusterMACSJ0647.7+7015 (at $z=0.591$). Our lens model uses the 9 sets of multipleimages, including those of MACS0647-JD, identified by the CLASH survey towardsthis cluster. We convincingly exclude the low redshift regime of $z<3$, forwhich convoluted critical curves are generated by our method, as the solutionbends to accommodate the wide angles of MACS0647-JD for this low redshift.Instead, a best fit to all sets of lensed galaxy positions and redshiftsprovides a geometric redshift of $z\simeq 10.8^{+0.3}_{-0.4}$ for MACS0647-JD,strongly supporting the higher photometric redshift solution. Importantly, wefind a tight linear relation between the relative brightnesses of all 9 sets ofmultiply lensed images and their relative magnifications as predicted by ourmodel. This agreement provides a benchmark for the quality of the lens model,and establishes the robustness of our free-form lensing method for measuringmodel-independent geometric source distances and for deriving objective centralcluster mass distributions. After correcting for its magnification theluminosity of MACS0647-JD remains relatively high at $M_{UV}=-19.4$, which iswithin a factor of a few in flux of some surprisingly luminous $z\simeq10$--$11$ candidates discovered recently in Hubble black field surveys.

Geometric Corroboration of the Earliest Lensed Galaxy at z~10.8 from Robust Free-Form Modelling