{\Lambda}CDM with baryons vs. MOND: the time evolution of the universal acceleration scale in the Magneticum simulations

TL;DR

This study demonstrates that cosmological simulations based on the DM model can reproduce MOND-like acceleration relations in galaxies and predicts that the universal acceleration scale a_0 increases with redshift, providing a testable difference between models.

Contribution

It shows that DM simulations can produce MOND-like relations and predicts the evolution of the acceleration scale a_0 over cosmic time.

Findings

DM simulations reproduce MOND-like acceleration relations.

The acceleration scale a_0 increases by a factor of rom redshift 0 to 2.

Provides a cosmological test to distinguish DM from MOND.

Abstract

MOdified Newtonian Dynamics (MOND) is an alternative to the standard Cold Dark Matter (CDM) paradigm which proposes an alteration of Newton's laws of motion at low accelerations, characterized by a universal acceleration scale a_0. It attempts to explain observations of galactic rotation curves and predicts a specific scaling relation of the baryonic and total acceleration in galaxies, referred to as the Rotational Acceleration Relation (RAR), which can be equivalently formulated as a Mass Discrepancy Acceleration Relation (MDAR). The appearance of these relations in observational data such as SPARC has lead to investigations into the existence of similar relations in cosmological simulations using the standard {\Lambda}CDM model. Here, we report the existence of an RAR and MDAR similar to that predicted by MOND in {\Lambda}CDM using a large sample of galaxies extracted from a cosmological, hydrodynamical simulation (Magneticum). Furthermore, by using galaxies in Magneticum at different redshifts, a prediction for the evolution of the inferred acceleration parameter a_0 with cosmic time is derived by fitting a MOND force law to these galaxies. In Magneticum, the best fit for a_0 is found to increase by a factor of approximately 3 from redshift z = 0 to z = 2. This offers a powerful test from cosmological simulations to distinguish between MOND and {\Lambda}CDM observationally.