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Harvard ADS: JWST NIRSpec Spectroscopy of the Triply Lensed z = 10.17 Galaxy MACS0647–JD

Paper abstract: We present JWST/NIRSpec prism spectroscopy of MACS0647-JD, a triply lensed z ~ 11 candidate discovered in Hubble Space Telescope imaging and spatially resolved by JWST imaging into two components, A and B. Spectroscopy of component A yields a spectroscopic redshift z = 10.17 based on seven detected emission lines: C III] ? ?1907, 1909, [O II] ?3727, [Ne III] ?3869, [Ne III] ?3968, Hd ?4101, H? ?4340, and [O III] ?4363. These are the second-most distant detections of these emission lines to date, in a galaxy observed just 460 million years after the Big Bang. Based on observed and extrapolated line flux ratios we derive a gas-phase metallicity 12 + log(O/H) ~ 7.5–8.0, or Z ~ (0.06–0.2) Z _?, ionization parameter = -1.9 ± 0.2, and an ionizing photon production efficiency erg^-1 Hz. The spectrum has a softened Lya break, evidence for a strong Lya damping wing. The Lya damping wing also suppresses the F150W photometry, explaining the slightly overestimated photometric redshift z = 10.6 ± 0.3. MACS0647-JD has a stellar mass log(M/M _?) = 8.1 ± 0.3, including ~6 × 10⁷ M _? in component A, most of which formed recently (within ~20 Myr) with a star formation rate ~ 2 ± 1 M _? yr^-1, all within an effective radius 70 ± 24 pc. Spectroscopy of a fainter companion galaxy C separated by a distance of ~ 3 kpc reveals a Lyman break consistent with z ~ 10.17. MACS0647-JD is likely the most distant galaxy merger known.