James Webb Space Telescope Feed Post

Harvard ADS: JADES: Physical properties of Ly\alpha and non-Ly\alpha emitters at z ~ 4.8-9.6

Paper abstract: We investigate the physical properties of Lyman-alpha emitters (LAEs) and non-Lyman-alpha emitters (non-LAEs) at z~4.8--9.6 via a stacking analysis of 253 JWST/NIRSpec spectra of galaxies observed as part of the JWST Advanced Deep Extragalactic Survey (JADES). We identify a sample of 42 LAEs with the equivalent width of Ly\alpha \gtrsim20\AA and a sample of 211 non-LAEs, divide each sample further via the median redshift of the LAEs (z~6.3), and create composite spectra using the low and medium resolution spectra from NIRSpec. We estimate physical quantities such as dust extinction, UV continuum slope \beta, electron temperatures, ionization parameter, escape fraction of Ly\alpha and Lyman Continuum, and the photon production rate for each bin/stack. The existing dust-extinction laws do not appear to be valid at these epochs. The emission line ratio analyses show that active galactic nuclei might dominate all sub-samples, irrespective of Ly\alpha emission. LAEs show much higher [OIII]/[OII] and low [OII]/H\delta at z<~6.3 compared to non-LAEs, but these line ratios are not sufficient to distinguish the two populations at z>6.3. However, the LAEs samples show large EW([OIII]4959, 5007) (>1000\AA) compared to the non-LAEs sample at all redshifts. CIV/Ly\alpha and CIV/CIII] for LAE population at z<~6.3 is ~a factor of 5 larger than that for LAE population at z>6.3. The ionizing radiation for LAEs is hard, as revealed from several diagnostics, including CIV detection, high [OIII]/[OII] (>8), and large values of \xi^{*}_{ion}.