James Webb Space Telescope Feed Post

Arxiv: JWST/NIRSpec Observations of Lyα Emission in Star Forming Galaxies at 6.5\lesssim z\lesssim13 Published: 8/2/2024 9:06:16 PM Updated: 9/17/2024 2:50:08 AM

Paper abstract: We present an analysis of JWST Ly\alpha spectroscopy of z\gtrsim6.5galaxies, using observations in the public archive covering galaxies in fourindependent fields (GOODS-N, GOODS-S, Abell 2744, EGS). We measure Ly\alphaemission line properties for a sample of 210 z~eq6.5-13 galaxies, withredshifts confirmed independently of Ly\alpha in all cases. We present 3new detections of Ly\alpha emission in JWST spectra, including a largeequivalent width (EW =143\ \r{A}) Ly\alpha emitter with strong CIV emission(EW =21\ \r{A}) at z=7.1 in GOODS-N. We measure the redshift-dependentLy\alpha EW distribution across our sample. We find that strong Ly\alphaemission (EW >25\ \r{A}) becomes increasingly rare at earlier epochs,suggesting that the transmission of Ly\alpha photons decreases by 4\timesbetween z~eq5 and z~eq9. We describe potential implications for theIGM neutral fraction. There is significant field to field variance in theLy\alpha emitter fraction. In contrast to the three other fields, the EGSshows no evidence for reduced transmission of Ly\alpha photons atz~eq7-8, suggesting a significantly ionized sightline may be present inthe field. We use available NIRCam grism observations from the FRESCO survey tocharacterize overdensities on large scales around known Ly\alpha emitters inthe GOODS fields. The strongest overdensities appear linked with extremelystrong Ly\alpha detections (EW >50\ \r{A}) in most cases. Future Ly\alphaspectroscopy with JWST has the potential to constrain the size of ionizedregions around early galaxy overdensities, providing a new probe of thereionization process.