COSMOS-Web: stellar mass assembly in relation to dark matter halos across $0.2<z<12$ of cosmic history

Understand

We study the stellar mass function (SMF) and the co-evolution with dark matter halos via abundance matching in the largest redshift range to date $0.2<z<12$ in $0.53 \, {\rm deg}^2$ imaged by JWST from the COSMOS-Web survey.

• At $z>5$, we find increased abundances of massive (log$\, M_{\star}/M_{\odot}>10.5$) implying integrated star formation efficiencies (SFE) $\epsilon_{\star}\equiv M_{\star}\, f_{\rm b}^{-1} M_{\rm halo}^{-1} \gtrsim 0.5$.
• We find a flattening of the SMF at the high-mass end that is better described by a double power law at $z>5.5$.
• At $z \lesssim 5.5$ it transitions to a Schechter law which coincides with the emergence of the first massive quiescent galaxies in the Universe.