The MOND Fundamental Plane

TL;DR

This paper demonstrates that Modified Newtonian Dynamics (MOND) can successfully fit the velocity dispersion data of early-type galaxies and predict a fundamental plane relation, offering an alternative to dark matter-based models.

Contribution

It shows that MOND can reproduce the fundamental plane of early-type galaxies, extending its applicability beyond spiral galaxies and dark matter frameworks.

Findings

MOND fits observed central velocity dispersions of ETGs.

MOND predicts a fundamental plane relation among galaxy parameters.

A tilt exists between observed and MOND-predicted fundamental planes.

Abstract

Modified Newtonian Dynamics (MOND) has been shown to be able to fit spiral galaxy rotation curves as well as giving a theoretical foundation for empirically determined scaling relations, such as the Tully - Fisher law, without the need for a dark matter halo. As a complementary analysis, one should investigate whether MOND can also reproduce the dynamics of early - type galaxies (ETGs) without dark matter. As a first step, we here show that MOND can indeed fit the observed central velocity dispersion $\sigma_0$ of a large sample of ETGs assuming a simple MOND interpolating functions and constant anisotropy. We also show that, under some assumptions on the luminosity dependence of the Sersic n parameter and the stellar M/L ratio, MOND predicts a fundamental plane for ETGs : a log - linear relation among the effective radius $R_{eff}$, $\sigma_0$ and the mean effective intensity $\langle I_e \rangle$. However, we predict a tilt between the observed and the MOND fundamental planes.