Super-early JWST galaxies, outflows, and Lyαvisibility in the Epoch of Reionization

Abstract

The overabundance of super-early (redshift $z>10$) luminous ($M_ UV < -20$) blue galaxies detected by JWST has been explained as being due to negligible dust attenuation in these systems. We show that this 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 (sSFR) grows as $ sSFR $. At $z 10$, the cosmic sSFR crosses the critical value $ sSFR^ $, and approximately $45$<!PCT!> of the galaxies become super-Eddington, driving outflows reaching velocities of $ where $ and $f_M$ are the star formation 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 Lyalpha line from $z>10$ galaxies by introducing a velocity offset. The observed Lyalpha properties in GN-z11 ($z=10.6$) are simultaneously recovered by the outflow model if $ HI 20.1$, implying that the outflow is largely ionized. We make analogous predictions for the Lyalpha visibility of other super-early galaxies, and we compare the model with Lyalpha surveys at $z>7$, finding that essentially all super-Eddington (sub-Eddington) galaxies are (not) detected in Lyalpha . Finally, the sSFR positively correlates with the LyC escape fraction, as outflows carve ionized transparent channels through which LyC photons leak.

Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic Star Formation Rate Density 300 Myr after the Big Bang

“…For instance, the feedback-free models of Dekel et al (2023) and Li et al (2023) agree with our z ∼ 12 observations for an efficiency of »  0.2 max . Models for the evolving number counts of high-redshift galaxies based on dust-free populations (e.g., Ferrara et al 2023) also predict an SFR density evolution to z ∼ 15 in agreement with our inferences, assuming all our candidates are really high-redshift sources (Ferrara 2024).…”

The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5

“…Evolving their model to higher redshifts, they naturally predict a slowing in the evolution of the UV luminosity function from z ∼ 9 to 11 due to significantly reduced attenuation in galaxies. This arises in their model owing to outflows driven by very high ("super-Eddington") specific SFRs, which can efficiently drive gas (and dust) out from these galaxies (Ferrara 2024). They discuss that this is supported by the data, as early results on the colors of z > 8 galaxies showed that they were fairly blue (e.g., Finkelstein et al 2022b;Topping et al 2022;Cullen et al 2023;Papovich et al 2023) and thus likely contained little dust.…”

The Interplay between the Initial Mass Function and Star Formation Efficiency through Radiative Feedback at High Stellar Surface Densities

“…Alternatively, another possibility to reconcile our high cloudscale SFE values with relatively lower ò *,gal is that only a fraction of the gas in the galaxy participates in star formation in clouds. It is possible that the remaining gas is ejected in outflows by the feedback from older stellar populations, possibly explaining the dust-free nature of these galaxies (Ferrara 2024;Ferrara et al 2023;Fiore et al 2023), which is likely critical to simultaneously explain the observed UV luminosity functions and the blue UV continuum slopes (e.g., Cullen et al 2024)-although see Li et al (2023) for an alternative explanation of these findings. This possibility raises another effect of a top-heavy IMF that we cannot capture in our simulations: a top-heavy IMF 15 would lead to more energy and mass-loaded winds, potentially further decreasing ò *,gal , such that its combination with a top-heavy IMF could be consistent with the observations.…”