Investigating the radial acceleration relation in early-type galaxies using the Jeans analysis

TL;DR

This study examines the radial acceleration relation in early-type galaxies using Jeans analysis, revealing that only a subset follow the spiral galaxy RAR, with implications for dark matter and modified gravity theories.

Contribution

It introduces a method to analyze the gravitational field in ETGs using kinematic profiles and Jeans equations, highlighting differences from spiral galaxies and challenging MOND assumptions.

Findings

Few ETGs follow the spiral galaxy RAR.

Fast rotators with disky isophotes tend to follow the RAR.

Most ETGs deviate, suggesting alternative explanations.

Abstract

Investigating the gravitational field in the early-type galaxies (ETGs, i.e. ellipticals and lenticulars) up to large radii is observationally difficult. It is questionable how the radial acceleration (RAR) in the ETGs looks like, i.e. the relation between the dynamically inferred gravitational acceleration and the acceleration expected from the distribution of the visible matter. This relation is nearly universal for the spiral galaxies, in agreement with the MOND modified dynamics paradigm. In this contribution, we investigate a sample of 15 ETGs. We extract their full kinematic profiles out to several effective radii from their globular cluster systems and estimate their gravitational field using the Jeans equation. We parametrize the gravitational field by that produced by the stars and a Navarro-Frenk-White DM halo. We find that only 4-5 of our ETGs follow the RAR for the spiral galaxies. All these galaxies are fast rotators, have disky isophotes, appear mostly very elongated and the have bluest colors in our sample. This suggests that they might be spiral galaxies which lost their gas. Our galaxies deviating from the RAR for the spirals either disprove MOND, contain unobserved matter, or indicate a flaw in the method.