Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Nimisha Kumari, Renske Smit, Joris Witstok, Marco Sirianni, Roberto Maiolino
| Summary:
We investigate the physical properties of Lyman-alpha emitters (LAEs) and
non-Lyman-alpha emitters (non-LAEs) at z$sim$4.8–9.6 via a stacking analysis
of 253 JWST/NIRSpec spectra of galaxies observed as part of the JWST Advanced
Deep Extragalactic Survey (JADES). We identify a sample of 42 LAEs with the
equivalent width of Ly$alpha$ $gtrsim$20AA 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$lesssim$6.3 compared to
non-LAEs, but these line ratios are not sufficient to distinguish the two
populations at z$>$6.3. However, the LAEs samples show large EW([OIII]4959,
5007) ($>$1000AA) compared to the non-LAEs sample at all redshifts.
CIV/Ly$alpha$ and CIV/CIII] for LAE population at z$lesssim$6.3 is $sim$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 $xi^{star}_{ion}$.
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