Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Gareth C. Jones, Andrew J. Bunker, Aayush Saxena, Joris Witstok, Daniel P. Stark
| Summary:
The rest-frame UV recombination emission line Ly$alpha$ can be powered by
ionising photons from young massive stars in star forming galaxies, but its
ability to be resonantly scattered by neutral gas complicates its
interpretation. For reionization era galaxies, a neutral intergalactic medium
(IGM) will scatter Ly$alpha$ from the line of sight, making Ly$alpha$ a
useful probe of the neutral fraction evolution. Here, we explore Ly$alpha$ in
JWST/NIRSpec spectra from the ongoing JADES programme, which targets hundreds
of galaxies in the well-studied GOODS-S and GOODS-N fields. These sources are
UV-faint ($-20.4<rm M_{rm UV}<-16.4$), and thus represent a poorly-explored
class of galaxies. The low spectral resolution ($Rsim100$) spectra of a subset
of 84 galaxies in GOODS-S with $z_{spec}>5.6$ (as derived with optical lines)
are fit with line and continuum models, in order to search for significant line
emission. Through exploration of the R100 data, we find evidence for Ly$alpha$
in 17 sources. This sample allows us to place observational constraints on the
fraction of galaxies with Ly$alpha$ emission in the redshift range
$5.6<z<7.5$, with a decrease from $z=6$ to $z=7$. We also find a positive
correlation between Ly$alpha$ equivalent width and M$_{UV}$, as seen in other
samples. These results are used to estimate the neutral gas fraction at
$zsim7$, agreeing with previous results ($X_{HI}sim0.5-0.9$).
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