The HST-Hyperion Survey: Grism Observations of a $z\sim2.5$ Proto-Supercluster

Ben Forrest; Lu Shen; Brian C. Lemaux; Ekta Shah; Olga Cucciati; Roy R. Gal; Finn Giddings; Emmet Golden-Marx; Weida Hu; Kaila Ronayne; Derek Sikorski; Priti Staab; Ricardo O. Amorín; Sandro Bardelli; Bianca Garilli; Nimish Hathi; Denise Hung; Lori Lubin; Debora Pelliccia; Russell E. Ryan; Gianni Zamorani; Elena Zucca

arXiv · 2503.04884

The HST-Hyperion Survey: Grism Observations of a $z\sim2.5$ Proto-Supercluster

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Abstract

We present first results and catalogs from the HST-Hyperion survey. This survey has collected 50 orbits of WFC3/F160W imaging and WFC3/G141 grism spectroscopy in the most overdense regions of the Hyperion proto-supercluster at $z\sim2.45$, which are analyzed in conjunction with the adjacent 56 orbits of WFC3/F140W imaging and WFC3/G141 grism spectroscopy from the 3D-HST survey. Sources were identified and spectra extracted using GRIZLI, which subsequently fit the combined grism data with object-matched photometric data from the COSMOS2020 catalog to obtain a redshift and best-fit spectral model. Each source was then visually inspected by multiple team members and quality flags were assigned. A total of 12814 objects with $m_{HST} \leq 25.0$ were inspected, of which 5629 (44%) have reliable redshifts from the grism data, which are sensitive to emission lines at a level of $\sim8.8 \times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ ($1\sigma$). Comparison to high-quality ground-based spectroscopic redshifts yields a scatter of $\sigma_{\rm NMAD} = 0.0016$. The resulting catalogs contain 125 confirmed members of the Hyperion structure within $2.40<z<2.53$, with an additional 71 confirmed galaxies in projection within $2.35<z<2.65$. The redshift, stellar population, and line flux catalogs, as well as all grism spectra, are publicly available.

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Ben Forrest, Lu Shen, Brian C. Lemaux, Ekta Shah, Olga Cucciati, Roy R. Gal, Finn Giddings, Emmet Golden-Marx, Weida Hu, Kaila Ronayne, Derek Sikorski, Priti Staab, Ricardo O. Amorín, Sandro Bardelli, Bianca Garilli, Nimish Hathi, Denise Hung, Lori Lubin, Debora Pelliccia, Russell E. Ryan, Gianni Zamorani, Elena Zucca. 2025-03-06. The HST-Hyperion Survey: Grism Observations of a $z\sim2.5$ Proto-Supercluster. https://arxiv.org/abs/2503.04884

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