On the Orbital Velocity of Isolated Galaxy Pairs: a test of gravity in the low acceleration regime

TL;DR

This paper investigates galaxy pair velocities to test gravity theories, finding a preferred velocity region that challenges standard models but aligns with Modified Newtonian Dynamics predictions.

Contribution

It demonstrates that observed galaxy pair velocities support Modified Newtonian Dynamics over standard cosmological simulations.

Findings

Discovery of a preferred velocity region at ~150 km/s in galaxy pairs

Standard simulations struggle to explain the observed velocity feature

Modified Newtonian Dynamics predicts a similar velocity peak at ~170 km/s

Abstract

The dynamics of isolated galaxy pairs represents an important tool to investigate the behavior of gravity in the low acceleration regime. Statistical analysis of a large sample of galaxy pairs led to the noticeable discovery of a region of preferred 3-dimensional velocities centered at $\sim 150$ km/s and $\sim 100$ km/s wide, a feature hard to justify in the context of numerical simulations of cosmological structure formation. It is shown here that such a feature is expected within the framework of the Modified Newtonian Dynamics, which, however, predicts it to be centered at $\sim$ 170 Km/s.