Ly$\alpha$ emission in galaxies at $z\simeq5-6$: new insight from JWST into the statistical distributions of Ly$\alpha$ properties at the end of reionization
| Autor: | Tang, Mengtao, Stark, Daniel P., Ellis, Richard S., Sun, Fengwu, Topping, Michael, Robertson, Brant, Tacchella, Sandro, Arribas, Santiago, Baker, William M., Bhatawdekar, Rachana, Boyett, Kristan, Bunker, Andrew J., Charlot, Stéphane, Chen, Zuyi, Chevallard, Jacopo, Jones, Gareth C., Kumari, Nimisha, Lyu, Jianwei, Maiolino, Roberto, Maseda, Michael V., Saxena, Aayush, Whitler, Lily, Williams, Christina C., Willott, Chris, Witstok, Joris |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | JWST has recently sparked a new era of Ly$\alpha$ spectroscopy, delivering the first measurements of the Ly$\alpha$ escape fraction and velocity profile in typical galaxies at $z\simeq6-10$. These observations offer new prospects for insight into the earliest stages of reionization. But to realize this potential, we need robust models of Ly$\alpha$ properties in galaxies at $z\simeq5-6$ when the IGM is mostly ionized. Here we use new JWST observations from the JADES and FRESCO surveys combined with VLT/MUSE and Keck/DEIMOS data to characterize statistical distributions of Ly$\alpha$ velocity offsets, escape fractions, and EWs in $z\simeq5-6$ galaxies. We find that galaxies with large Ly$\alpha$ escape fractions (> 0.2) are common at $z\simeq5-6$, comprising 30 per cent of Lyman break selected samples. Comparing to literature studies, our census suggests that Ly$\alpha$ becomes more prevalent in the galaxy population toward higher redshift from $z\sim3$ to $z\sim6$, although we find that this evolution slows considerably between $z\sim5$ and $z\sim6$, consistent with modest attenuation from residual HI in the mostly ionized IGM at $z\simeq5-6$. We find significant evolution in Ly$\alpha$ velocity profiles between $z\simeq2-3$ and $z\simeq5-6$, likely reflecting the influence of resonant scattering from residual intergalactic HI on the escape of Ly$\alpha$ emission near line center. This effect will make it challenging to use Ly$\alpha$ peak offsets as a probe of Lyman continuum leakage at $z\simeq5-6$. We use our $z\simeq5-6$ Ly$\alpha$ distributions to make predictions for typical Ly$\alpha$ properties at $z\gtrsim8$ and discuss implications of a recently-discovered Ly$\alpha$ emitter at $z\simeq8.5$ with a small peak velocity offset (156 km s$^{-1}$). Comment: 31 pages, 12 figures, accepted by MNRAS |
| Databáze: | arXiv |
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