James Webb Space Telescope Feed Post

Harvard ADS: Lyman-\alpha feedback prevails at Cosmic Dawn: Implications for the first galaxies, stars, and star clusters

Paper abstract: Radiation pressure from Lyman-\alpha (Ly\alpha) scattering is a potentially dominant form of early stellar feedback, capable of injecting up to ~ 100 \, \times more momentum into the interstellar medium (ISM) than UV continuum radiation pressure and stellar winds. Ly\alpha feedback is particularly strong in dust-poor environments and is thus especially important during the formation of the first stars and galaxies. As upcoming galaxy formation simulations incorporate Ly\alpha feedback, it is crucial to consider processes that can limit it to avoid placing \LambdaCDM in apparent tension with recent \textit{JWST} observations indicating efficient star formation at Cosmic Dawn. We study Ly\alpha feedback using a novel analytical Ly\alpha radiative transfer solution that includes the effects of continuum absorption, gas velocity gradients, Ly\alpha destruction (e.g. by 2p \rightarrow 2s transitions), ISM turbulence, and atomic recoil. We verify our solution for uniform clouds using extensive Monte Carlo radiative transfer (MCRT) tests, and resolve a previous discrepancy between analytical and MCRT predictions. We then study the sensitivity of Ly\alpha feedback to the aforementioned effects. While these can dampen Ly\alpha feedback by a factor <~ \textrm{few} \times 10, we find it remains \gtrsim 5 - 100 \, \times stronger than direct radiation pressure and therefore cannot be neglected. We provide an accurate fit for the Ly\alpha force multiplier M_{\rm F}, suitable for implementation in subgrid models for galaxy formation simulations. Our findings highlight the critical role of Ly\alpha feedback in regulating star formation at Cosmic Dawn, and underscore the necessity of incorporating it into simulations to accurately model early galaxy evolution.