The empirical laws of galaxy dynamics: from gas kinematics to weak lensing

TL;DR

This paper reviews recent weak lensing studies revealing universal empirical laws of galaxy dynamics, such as flat rotation curves, the baryonic Tully-Fisher relation, and the radial acceleration relation, consistent with MOND predictions.

Contribution

It synthesizes observational evidence from weak lensing across galaxy types, demonstrating the universality of these empirical laws and their alignment with MOND theory.

Findings

Flat rotation curves extend to hundreds of kpc.

Baryonic Tully-Fisher relation is universal for LTGs and ETGs.

Radial acceleration relation spans 16 orders of magnitude.

Abstract

Galaxies obey a set of strict dynamical laws, which imply a close coupling between the visible matter (stars and gas) and the observed dynamics (set by dark matter in the standard cosmological context). Here we review recent results from weak gravitational lensing, which allows studying the empirical laws of galaxy dynamics out to exceedingly large radii in both late-type galaxies (LTGs) and early-type galaxies (ETGs). We focus on three laws: (1) the circular velocity curves of both LTGs and ETGs remain indefinitely flat out to several hundreds of kpc; (2) the same baryonic Tully-Fisher relation is followed by LTGs and ETGs; (3) the same radial acceleration relation (RAR) is followed by LTGs and ETGs. Combining galaxy data with Solar System data, the RAR covers about 16 orders of magnitude in the Newtonian baryonic acceleration. Remarkably, these empirical facts were predicted a priori by MOND.