Abstract
We describe new JWST/NIRSpec observations of galaxies at z greater than or similar to 7 taken from the CEERS survey. Previous observations of this area have revealed associations of Ly alpha emitters at redshifts (z = 7.5, 7.7, and 8.7) where the intergalactic medium (IGM) is thought to be mostly neutral, leading to suggestions that these systems are situated in large ionized bubbles. We identify 21 z greater than or similar to 7 galaxies with robust redshifts in the CEERS data set, including 10 in the Ly alpha associations. Their spectra are indicative of very highly ionized and metal poor gas, with line ratios (O32 = 17.84 and Ne3O2 = 0.89, linear scale) and metallicity (12+log (O/H)=7.84) that are rarely seen at lower redshifts. We find that the most extreme spectral properties are found in the six z greater than or similar to 7 Ly alpha emitters in the sample. Each has a hard ionizing spectrum indicating that their visibility is likely enhanced by efficient ionizing photon production. Ly alpha velocity offsets are found to be very large (greater than or similar to 300 km s(-1)), likely also contributing to their detectability. We find that Ly alpha in z greater than or similar to 7 galaxies is 6-12 x weaker than in lower redshift samples with matched rest-optical spectral properties. If the bubbles around the Ly alpha emitters are relatively small (less than or similar to 0.5-1 pMpc), we may expect such significant attenuation of Ly alpha in these ionized regions. We discuss several other effects that may contribute to weaker Ly alpha emission at z greater than or similar to 7. Deep spectroscopy of fainter galaxies in the vicinity of the Ly alpha emitters will better characterize the physical scale of the ionized bubbles in this field.