The Fast and Furious in JWST high-$z$ galaxies

Abstract

Recent JWST surveys reveal a striking abundance of massive galaxies at cosmic dawn, earlier than predicted by $\Lambda$CDM. The implied speed-up in galaxy formation by gravitational collapse is reminiscent of short-period galaxy dynamics described by the baryonic Tully-Fisher relation. This may originate in weak gravitation tracking the de Sitter scale of acceleration $a_{dS}=cH$, where $c$ is the velocity of light and $H(z)\propto \left(1+z\right)^{3/2}$ is the Hubble parameter with redshift $z$. With no free parameters, this produces a speed-up in early galaxy formation by an order of magnitude with essentially no change in initial galaxy mass function. It predicts a deceleration parameter $q_0=1-\left( 2\pi/GAa_{dS}\right)^2 = -0.98\pm 0.5$, where $G$ is Newton's constant and $A=(47\pm6)M_\odot$\,(km/s)$^{-4}$ is the baryonic Tully-Fisher coefficient (McGaugh 2012). At $3\sigma$ significance, it identifies dynamical dark energy alleviating $H_0$-tension when combined with independent $q_0$ estimates in the Local Distance Ladder. Conclusive determination of $q_0=d\log(\theta(z)H(z))/dz\left|_{z=0}\right.$ is expected from BAO angle $\theta(z)$ observations by the recently launched {\em Euclid} mission.