Аннотация
The demographics of the production and escape of ionizing photons from
UV-faint early galaxies is a key unknown in discovering the primary drivers of
reionization. With the advent of JWST it is finally possible to observe the
rest-frame optical nebular emission from individual sub-L$^*$ z>3 galaxies to
measure the production of ionizing photons, $\xi_ion$. Here we study a
sample of 380 z~3-7 galaxies spanning -23 <M$_UV$ < -15.5 (median
M$_UV\approx$ -18) with deep multi-band HST and JWST/NIRCam photometry
covering the rest-UV to optical from the GLASS and UNCOVER JWST surveys. Our
sample includes 109 galaxies with Lyman-alpha emission detected in MUSE
spectroscopy. We use H-alpha fluxes inferred from NIRCam photometry to estimate
the production rate of ionizing photons which do not escape these galaxies
$\xi_ion(1-f_esc)$. We find median
$łog_10\xi_ion(1-f_esc)=25.330.47$, with a broad
intrinsic scatter 0.42 dex, implying a broad range of galaxy properties and
ages in our UV-faint sample. Galaxies detected with Lyman-alpha have ~0.1 dex
higher $\xi_ion(1-f_esc)$, which is explained by their higher
H-alpha EW distribution, implying younger ages, higher sSFR and thus more O/B
stars. We find significant trends of increasing
$\xi_ion(1-f_esc)$ with increasing H-alpha EW, decreasing UV
luminosity, and decreasing UV slope, implying the production of ionizing
photons is enhanced in young, low metallicity galaxies. We find no significant
evidence for sources with very high ionizing escape fraction
($f_esc$>0.5) in our sample, based on their photometric properties,
even amongst the Lyman-alpha selected galaxies. This work demonstrates that
considering the full distribution of $\xi_ion$ across galaxy
properties is important for assessing the primary drivers of reionization.
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