2025/10/29 by Manzoni, D., Ferrara, A.
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2510.25950
Order-unity star formation efficiencies (SFE) in early galaxies may explain the overabundance of bright galaxies observed by JWST at high redshift. Here we show that Lyman-α (Lyα) radiation pressure limits the gas mass converted into stars, particularly in primordial environments. We develop a shell model including Lyα feedback, and validate it with one-dimensional hydrodynamical simulations. To account for Lyα resonant scattering, we adopt the most recent force multiplier fits, including the effect of Lyα photon destruction by dust grains. We find that, independently of their gas surface density Σg, clouds are disrupted on a timescale shorter than a free-fall time, and even before supernova explosions if Σg \gtrsim 103 M\odot \rm pc-2. At log(Z/Z\odot) = -2, relevant for high-redshift galaxies, the SFE is 0.01 \lesssim ε* \lesssim 0.66 for 103 \lesssimΣg [M\odot \rm pc-2] \lesssim 105. The SFE is even lower for decreasing metallicity. Near-unity SFEs are possible only for extreme surface densities, Σg \gtrsim 105 M\odot \rm pc-2, and near-solar metallicities. We conclude that Lyα radiation pressure severely limits a possible extremely efficient, feedback-free phase of star formation in dense, metal-poor clouds.