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arXiv · 2605.01095

Validating z > 7.5 Lyman Break Galaxy candidates in the COSMOS field with JWST/PASSAGE

Zoke W. Sackih·Mason S. Huberty·Claudia Scarlata·Peter J. Watson·Andrew J. Battisti·Farhanul Hasan·Matthew J. Hayes·Matthew A. Malkan·Vihang Mehta·Kalina V. Nedkova·Marc Rafelski·Benedetta Vulcani
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Abstract

We analyze spectroscopy from one NIRISS pointing in the JWST-PASSAGE program for seven candidate $z \gtrsim 7.5$ photometrically-selected COSMOS-Web sources. We spectroscopically confirm one out of seven sources as a Lyman break galaxy (LBG) at $z=7.962^{+0.003}_{-0.006}$, with $m_{F150W} = 25.9$ (AB). The remaining sources are too faint in the continuum (i.e., $m_{F150W} \gtrsim 26$ AB) to provide a redshift measurement from the Lyman break, and do not show emission lines in their spectra. Although this study contains only one spectroscopically confirmed source, the confirmation of a luminous $z \sim 8$ galaxy within this $\sim4.8$ arcmin$^2$ field implies a surface density of $\sim 0.21^{+0.59}_{-0.17}$ arcmin$^{-2}$, $\approx 10\times$ higher than inferred from wide-area photometric surveys, suggesting a potential overdensity at $z\sim8$ in the COSMOS field.

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Zoke W. Sackih, Mason S. Huberty, Claudia Scarlata, Peter J. Watson, Andrew J. Battisti, Farhanul Hasan, Matthew J. Hayes, Matthew A. Malkan, Vihang Mehta, Kalina V. Nedkova, Marc Rafelski, Benedetta Vulcani. 2026-05-01. Validating z > 7.5 Lyman Break Galaxy candidates in the COSMOS field with JWST/PASSAGE. https://arxiv.org/abs/2605.01095

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