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

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Main Authors: Worku, Keduse, Hsiao, Tiger Yu-Yang, Coe, Dan, Abdurro'uf, Resseguier, Tom, Larson, Rebecca L., Antwi-Danso, Jacqueline, Brammer, Gabriel, Kokorev, Vasily, Bradley, Larry D., Furtak, Lukas J., Oguri, Masamune
Format: Preprint
Published: 2025
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author Worku, Keduse
Hsiao, Tiger Yu-Yang
Coe, Dan
Abdurro'uf
Resseguier, Tom
Larson, Rebecca L.
Antwi-Danso, Jacqueline
Brammer, Gabriel
Kokorev, Vasily
Bradley, Larry D.
Furtak, Lukas J.
Oguri, Masamune
author_facet Worku, Keduse
Hsiao, Tiger Yu-Yang
Coe, Dan
Abdurro'uf
Resseguier, Tom
Larson, Rebecca L.
Antwi-Danso, Jacqueline
Brammer, Gabriel
Kokorev, Vasily
Bradley, Larry D.
Furtak, Lukas J.
Oguri, Masamune
contents 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-$α$. 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.
format Preprint
id arxiv_https___arxiv_org_abs_2512_11985
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle High-Redshift Galaxy Candidates at z > 6 as Revealed by JWST Observations of MACS0647
Worku, Keduse
Hsiao, Tiger Yu-Yang
Coe, Dan
Abdurro'uf
Resseguier, Tom
Larson, Rebecca L.
Antwi-Danso, Jacqueline
Brammer, Gabriel
Kokorev, Vasily
Bradley, Larry D.
Furtak, Lukas J.
Oguri, Masamune
Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
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-$α$. 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.
title High-Redshift Galaxy Candidates at z > 6 as Revealed by JWST Observations of MACS0647
topic Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2512.11985