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Early Results from GLASS-JWST. I: Confirmation of Lensed $z\geqslant7$ Lyman-Break Galaxies Behind the Abell 2744 Cluster With NIRISS

Authors :
Roberts-Borsani, Guido
Morishita, Takahiro
Treu, Tommaso
Brammer, Gabriel
Strait, Victoria
Wang, Xin
Bradac, Marusa
Acebron, Ana
Bergamini, Pietro
Boyett, Kristan
CalabrĂ³, Antonello
Castellano, Marco
Fontana, Adriano
Glazebrook, Karl
Grillo, Claudio
Henry, Alaina
Jones, Tucker
Malkan, Matthew
Marchesini, Danilo
Mascia, Sara
Mason, Charlotte
Mercurio, Amata
Merlin, Emiliano
Nanayakkara, Themiya
Pentericci, Laura
Rosati, Piero
Santini, Paola
Scarlata, Claudia
Trenti, Michele
Vanzella, Eros
Vulcani, Benedetta
Willott, Chris
Publication Year :
2022

Abstract

We present the first search for $z\geqslant7$, continuum-confirmed sources with NIRISS/WFS spectroscopy over the Abell 2744 Frontier Fields cluster, as part of the GLASS-JWST ERS survey. With $\sim15$ hrs of pre-imaging and multi-angle grism exposures in the F115W, F150W, and F200W filters, we describe the general data handling (i.e., reduction, cleaning, modeling, and extraction processes) and analysis for the GLASS-JWST survey. We showcase the power of JWST to peer deep into reionization, when most intergalactic hydrogen is neutral, by confirming two galaxies at $z=8.04\pm0.15$ and $z=7.90\pm0.13$ by means of their Lyman breaks. Fainter continuum spectra are observed in both the F150W and F200W bands, indicative of blue ($-1.69$ and $-1.33$) UV slopes and moderately-bright absolute magnitudes ($-20.37$ and $-19.68$ mag). We do not detect strong Ly$\alpha$ in either galaxy, but do observe tentative ($\sim2.7-3.8\sigma$) HeII$\lambda$1640 A, OIII]$\lambda\lambda$1661,1666 A, and NIII]$\lambda\lambda$1747,1749 A line emission in one, suggestive of low metallicity, star-forming systems with possible non-thermal contributions. These novel observations provide a first look at the extraordinary potential of JWST/NIRISS for confirming representative samples of bright $z\geqslant7$ sources in the absence of strong emission lines, and gain unprecedented insight into their contributions towards cosmic reionization.<br />Comment: Accepted for publication in ApJL on 1st September 2022, after minor modifications based on the referee report. 10 pages, 3 figures, 1 table

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2207.11387
Document Type :
Working Paper
Full Text :
https://doi.org/10.3847/2041-8213/ac8e6e