The Mass-Discrepancy Acceleration Relation: a Natural Outcome of Galaxy Formation in Cold Dark Matter halos

TL;DR

This study shows that galaxy formation in cold dark matter halos naturally produces a tight relation between total and baryonic acceleration, aligning with observations and supporting standard cosmological models.

Contribution

It demonstrates that the mass-discrepancy acceleration relation emerges naturally from galaxy formation simulations with varied feedback processes.

Findings

Galaxies follow a tight relation between total and baryonic acceleration.

Feedback variations shift galaxies along the relation, not across it.

A characteristic acceleration scale, g_dagger, is observed, where baryons dominate.

Abstract

We analyze the total and baryonic acceleration profiles of a set of well-resolved galaxies identified in the EAGLE suite of hydrodynamic simulations. Our runs start from the same initial conditions but adopt different prescriptions for unresolved stellar and AGN feedback, resulting in diverse populations of galaxies by the present day. Some of them reproduce observed galaxy scaling relations, while others do not. However, regardless of the feedback implementation, all of our galaxies follow closely a simple relationship between the total and baryonic acceleration profiles, consistent with recent observations of rotationally supported galaxies. The relation has small scatter: different feedback implementations -- which produce different galaxy populations -- mainly shift galaxies along the relation, rather than perpendicular to it. Furthermore, galaxies exhibit a characteristic acceleration, $g_{\dagger}$, above which baryons dominate the mass budget, as observed. These observations, consistent with simple modified Newtonian dynamics, can be accommodated within the standard cold dark matter paradigm.