TY - JOUR
T1 - GEOMETRIC CORROBORATION of the EARLIEST LENSED GALAXY at z ≃ 10.8 from ROBUST FREE-FORM MODELLING
AU - Chan, Brian M.Y.
AU - Broadhurst, Tom
AU - Lim, Jeremy
AU - Diego, Jose M.
AU - Zitrin, Adi
AU - Coe, Dan
AU - Ford, Holland C.
N1 - Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/1/20
Y1 - 2017/1/20
N2 - A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of z ≃ 10.7+0.6 -0.4 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 MUV = -19.4, which is within a factor of a few in flux of some surprisingly luminous z ≃10-11 candidates discovered recently in Hubble blank field surveys.
AB - A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of z ≃ 10.7+0.6 -0.4 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 MUV = -19.4, which is within a factor of a few in flux of some surprisingly luminous z ≃10-11 candidates discovered recently in Hubble blank field surveys.
KW - dark matter
KW - galaxies: high-redshift
KW - gravitational lensing: strong
UR - http://www.scopus.com/inward/record.url?scp=85011277195&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/835/1/44
DO - 10.3847/1538-4357/835/1/44
M3 - Review article
AN - SCOPUS:85011277195
SN - 0004-637X
VL - 835
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 44
ER -