First Statistical Detection of Cool Gas Outflows with JWST Towards Cosmic Dawn
Authors
Cheqiu Lyu
Haoran Yu
Enci Wang
Junxian Wang
Cheng Jia
Jie Song
Yangyao Chen
Jinyang Wang
Zeyu Chen
Chengyu Ma
Yifan Wang
Xu Kong
Abstract
Galactic-scale outflows are a crucial component of galaxy evolution, yet their properties in the early universe remain poorly constrained. We present the first statistical investigation of cool gas outflows in galaxies spanning a wide cosmic timeline from $z \approx 1$ to $z \approx 10$. Using thousands of public JWST/NIRSpec spectra, we employ a signal-to-noise weighted spectral stacking technique on the \ion{Mg}{2} $λ\lambda2796, 2803$ absorption doublet. We robustly detect blueshifted \ion{Mg}{2} absorption in all stellar mass and redshift bins. The outflow equivalent width exhibits a strong, positive correlation with stellar mass ($M_*$) at all epochs, increasing from $\sim 1$~Å at $M_* \approx 10^9~\mathrm{M}_\odot$ to over $3$~Å at $M_* > 10^{10.5}~\mathrm{M}_\odot$. Our work provides the first statistical constraints on cool outflows in the low-mass ($M_* \lesssim 10^{9.5}~\mathrm{M}_\odot$), high-redshift ($z > 3$) regime, vital for constraining feedback in the numerous progenitors of typical present-day galaxies. Crucially, the scaling relation between outflow properties and stellar mass shows no significant evolution at $z > 3$. This suggests a persistent, unevolving feedback mechanism governing the baryon cycle in the early universe, placing strong constraints on models that invoke a fundamental change in feedback physics at Cosmic Dawn, such as the feedback-free starburst model.
