High-Redshift Galaxy Candidates at z > 6 as Revealed by JWST Observations of MACS0647

Keduse Worku; Tiger Yu-Yang Hsiao; Dan Coe; Abdurro'uf; Tom Resseguier; Rebecca L. Larson; Jacqueline Antwi-Danso; Gabriel Brammer; Vasily Kokorev; Larry D. Bradley; Lukas J. Furtak; Masamune Oguri

arXiv · 2512.11985

High-Redshift Galaxy Candidates at z > 6 as Revealed by JWST Observations of MACS0647

Keduse Worku·Tiger Yu-Yang Hsiao·Dan Coe·Abdurro'uf·Tom Resseguier·Rebecca L. Larson·Jacqueline Antwi-Danso·Gabriel Brammer·Vasily Kokorev·Larry D. Bradley·Lukas J. Furtak·Masamune Oguri

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Abstract

We present a catalog of 57 high-redshift $z>6$ galaxy candidates, including 14 spectroscopic confirmations ($z = 6.10$ -- 9.25), 2 Little Red Dots ($z = 4.77$, 5.81), and 2 interlopers ($z = 3.23$, 3.72), based on \JWST\ NIRCam imaging (7 filters), NIRSpec spectroscopy (PRISM and G395H), and archival \HST\ imaging (17 filters) of the strong lensing galaxy cluster MACS0647. Our highest redshift confirmation ($z = 9.25$) is an Extremely Blue Galaxy (presented in~\citealt{Yanagisawa2024}), and here we identify a spectral turnover likely due to damped Lyman-$\alpha$. We identify an overdensity of galaxies with spectroscopic redshifts $z = 6.1$, confirming the $z \sim 6$ overdensity identified in \HST\ images. In one of these galaxies, our high-resolution G395H spectroscopy reveals two spatially resolved components with a velocity difference of $\sim$90 km/s; if these components are gravitationally bound, this would imply a dynamical mass on the order of $\sim 10^8\ M_\odot$ given their projected separation. We present spectral line fluxes, widths, and derived physical properties, including stellar masses ($10^8 - 10^9 \ \mathrm{M}_{\odot}$) and metallicities ($10\% - 40\% \ \mathrm{Z}_{\odot}$) for our spectroscopic sample. We note half of our NIRSpec data was obtained with standard 3-slitlet nods and half was obtained with single slitlets yielding similar results, demonstrating the power to observe more sources on a densely packed NIRSpec MSA.

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Keduse Worku, Tiger Yu-Yang Hsiao, Dan Coe, Abdurro'uf, Tom Resseguier, Rebecca L. Larson, Jacqueline Antwi-Danso, Gabriel Brammer, Vasily Kokorev, Larry D. Bradley, Lukas J. Furtak, Masamune Oguri. 2025-12-12. High-Redshift Galaxy Candidates at z > 6 as Revealed by JWST Observations of MACS0647. https://arxiv.org/abs/2512.11985

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