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Arxiv: The interstellar medium conditions of a strong Lya emitter at z = 8.279 revealed by JWST: a robust LyC leaker candidate at the Epoch of Reionization Published: 7/19/2024 1:58:37 PM Updated: 7/19/2024 1:58:37 PM

Paper abstract: Making use of JWST NIRSpec and NIRCam data, we conduct a detailed analysis ofthe spectroscopic and photometric properties of GN-z8-LAE, a strong Lya emitterat z=8.279. Our goal is to investigate the interstellar medium (ISM) physicalconditions that enable the Lya detection in this source at the Epoch ofReionization (EoR) and scrutinize GN-z8-LAE as an early reionizer. In broadagreement with previous results, we find that GN-z8-LAE is a young galaxy (age~ 10 Myr) with a low stellar mass (M* ~ 10^7.66 Msun), significantly lower thanthose of most Lya emitters known at similarly high redshifts. The derivedstellar mass and star formation rate surface densities are 355 Msun/pc^2 and 88Msun/yr/kpc^2, respectively. Our spectral analysis indicates that: the Lya linepeak has a small velocity offset 133+-72 km/s with respect to the galaxysystemic redshift; CIV] / CIII] ~ 3.3; the ISM is characterized by a hardionization field, although no signature of AGN is present. Moreover, we reportthe presence of NIII]1750 emission with super-solar N abundance, which makesGN-z8-LAE one of the first known cases of a simultaneous strong Lya andnitrogen emitter at the EoR. Based on all these properties, we apply a widerange of methods to constrain the absolute Lyman continuum escape fraction ofGN-z8-LAE, and find that it is >14% in all cases. Therefore, we conclude thatGN-z8-LAE is a robust candidate for a Lyman continuum (LyC) leaker at the EoRwhich is being caught at the moment of efficiently reionizing its surroundingmedium.