Super-early JWST galaxies, outflows and Lyman alpha visibility in the EoR

Abstract

The overabundance of super-early (redshift $z>10$), luminous ($M_{\rm UV} < -20$), and blue galaxies detected by JWST has been explained (Ferrara et al. 2023) as due to negligible dust attenuation in these systems. We show that such model correctly reproduces the UV luminosity function at $z>10$, and the star formation rate (SFR) density evolution. The model also predicts, in agreement with data, that the cosmic specific SFR grows as ${\rm sSFR} \propto (1+z)^{3/2}$. At $z \simeq 10$ the cosmic sSFR crosses the critical value $\rm sSFR^\star = 25\, \rm Gyr^{-1}$ and $\approx 45$% of the galaxies become super-Eddington driving outflows reaching velocities of $\approx 830 \,(\epsilon_\star/f_M)^{1/2}\, {\rm km\, s}^{-1}$, where $\epsilon_\star$ and $f_M$ are the SF efficiency and fraction of the halo gas expelled in the outflow, respectively. This prediction is consistent with the outflow velocities measured in 12 super-Eddington galaxies of the JWST/JADES sample. Such outflows clear the dust, thus boosting the galaxy luminosity. They also dramatically enhance the visibility of the Ly$\alpha$ line from $z>10$ galaxies, by introducing a velocity offset. The observed Ly$\alpha$ properties in GN-z11 ($z=10.6$) are simultaneously recovered by the outflow model if $\log N_{\rm HI} \simeq 20.1$, implying that the outflow is largely ionized. We make analogous predictions for the Ly$\alpha$ visibility of other super-early galaxies, and compare the model with Ly$\alpha$ surveys at $z>7$, finding that essentially all super-Eddington (sub-Eddington) galaxies are (not) detected in Ly$\alpha$. Finally, the sSFR positively correlates with the LyC escape fraction as outflows carve ionized, transparent channels through which LyC photons leak.