Can TeVeS avoid Dark Matter on galactic scales?

TL;DR

This paper investigates whether TeVeS, a relativistic modified gravity theory, can explain galactic lensing without dark matter, finding it generally requires additional dark matter except for specific parameter choices that conflict with rotation curve data.

Contribution

It provides a detailed relativistic analysis of gravitational lensing in TeVeS and evaluates its ability to avoid dark matter on galactic scales.

Findings

TeVeS generally requires dark matter to explain lensing.

A specific form of the TeVeS function mu(y) can reduce dark matter needs.

The same mu(y) form cannot fit both lensing and rotation curves.

Abstract

A fully relativistic analysis of gravitational lensing in TeVeS is presented. By estimating the lensing masses for a set of six lenses from the CASTLES database, and then comparing them to the stellar mass, the deficit between the two is obtained and analysed. Considering a parametrised range for the TeVeS function $mu(y)$, which controls the strength of the modification to gravity, it is found that on galactic scales TeVeS requires additional dark matter with the commonly used $mu(y)$. A soft dependence of the results on the cosmological framework and the TeVeS free parameters is discussed. For one particular form of $mu(y)$, TeVeS is found to require very little dark matter. This choice is however ruled out by rotation curve data. The inability to simultaneously fit lensing and rotation curves for a single form of $mu(y)$ is a challenge to a "no dark matter" TeVeS proposal.