Origins of luminous UV emissions from the ﬁrst galaxies at z = 15 - 10

The observed UV luminosity function at z ≧ 10 suggests the overabundance of UV-bright ($M_\mathrm{UV} < -20$) and massive galaxies in comparison to pre-JWST theoretical predictions (e.g. Harikane+24, Donnan+24, Perez-Gonzalez+23). Several scenarios can explain the tension (e.g. Inayoshi+22, Dekel+23, Li+23, Mason+23, Yung+24, Shen+23), one of which is dust clearing by radiation-driven outﬂows (Ferrara+23, 24). To test this scenario, I estimate the extent to which radiation pressure is enhanced in dusty gas. I ﬁnd that it is boosted by a factor of $\sim 180(Z/0.1Z_\odot)$ compared to the standard Eddington limit (Figure 1). I show that a few galaxies observed at z > 10 have luminosities exceeding the effective Eddington luminosity for a dusty medium and are likely in the dusty outﬂow phase, while the other 80% of observed galaxies at z > 10 may have already experienced a dusty outﬂow and expelled their dust by the time of observation.

Figure1: The ratio of classical and modified Eddington luminosity ($A = L_\mathrm{E} /L_\mathrm{E,mod}$) as a function of gas column density $N_\mathrm{H}$ and metallicity Z. The dashed circle represents the range of the observed values of $z > 10$ galaxies. We see the radiative pressure is boosted by a factor of ∼ 100 in that region.