$\require{ mediawiki-texvc}$Given the sensitivity of the resonant Lyman-$\mathrm{ \alpha}$ (Ly$\mathrm{ \alpha}$) transition to absorption by neutral hydrogen, observations of Ly$\mathrm{ \alpha}$ emitting galaxies (LAEs) have been widely used to probe the ionising capabilities of reionisation-era galaxies and their impact on the intergalactic medium (IGM). However, prior to JWST our understanding of the contribution of fainter sources and of ionised `bubbles' at earlier stages of reionisation remained uncertain. Here, we present the characterisation of three exceptionally distant LAEs at $z>8$, newly discovered by JWST/NIRSpec in the JADES survey. These three similarly bright ($M_\text{ UV} \approx -20\,\mathrm{ mag}$) LAEs exhibit small Ly$\mathrm{ \alpha}$ velocity offsets from the systemic redshift, $\Delta v_\mathrm{ Ly\alpha} \lesssim 200\,\mathrm{ km\,s^{ -1}}$, yet span a range of Ly$\mathrm{ \alpha}$ equivalent widths ($15\,\AA$, $31\,\AA$, and $132\,\AA$). The former two show moderate Ly$\mathrm{ \alpha}$ escape fractions ($f_\mathrm{ esc,Ly\alpha} \approx 10\%$), whereas Ly$\mathrm{ \alpha}$ escapes remarkably efficiently from the third ($f_\mathrm{ esc,Ly\alpha} \approx 72\%$), which moreover is very compact (half-light radius of $90\pm10\,\mathrm{ pc}$). We find these LAEs are low-mass galaxies dominated by very recent, vigorous bursts of star formation accompanied by strong nebular emission from metal-poor gas. We infer the two LAEs with modest $f_\mathrm{ esc,Ly\alpha}$, one of which reveals evidence for ionisation by an active galactic nucleus, may have reasonably produced small ionised bubbles preventing complete IGM absorption of Ly$\mathrm{ \alpha}$. The third, however, requires a $\sim 3\,\text{ physical Mpc}$ bubble, indicating faint galaxies have contributed significantly. The most distant LAEs thus continue to be powerful observational probes into the earlier stages of reionisation.
Categories: astro-ph.GA
