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Radial Acceleration Relation of ΛCDM Satellite Galaxies
Enrico Garaldi1, Emilio Romano-Díaz1, Cristiano Porciani1
1Argelander Institut für Astronomie, Auf dem Hügel 71, Bonn D-53121, Germany.
Physical Review Letters
|July 14, 2018
Summary
Dwarf galaxies may deviate from the radial acceleration relation (RAR) due to a larger scatter, not a different physical mechanism. This finding supports the standard cosmological model (Lambda Cold Dark Matter) over alternative gravity theories like MOND.
Area of Science:
- Cosmology
- Astrophysics
- Galaxy Formation
Background:
- The radial acceleration relation (RAR) describes a tight correlation between baryonic matter and gravitational acceleration in bright galaxies.
- Dwarf spheroidal satellite galaxies exhibit a larger scatter and potential deviation from the RAR, posing a challenge to current gravitational theories.
Purpose of the Study:
- To investigate whether dwarf spheroidal galaxies naturally follow the RAR within the standard cosmological model (Lambda Cold Dark Matter - ΛCDM).
- To provide robust theoretical predictions for testing gravity at low accelerations.
- To differentiate between ΛCDM and Modified Newtonian Dynamics (MOND) based on galaxy RAR behavior.
Main Methods:
- Utilizing high-resolution hydrodynamical simulations to model galaxy formation and evolution.
- Analyzing the radial acceleration relation across a range of galaxy types and redshifts.
- Comparing simulation predictions with observational data for dwarf spheroidal galaxies.
Main Results:
- ΛCDM simulations predict that satellite galaxies follow the same RAR as brighter systems but with a larger, uncorrelated scatter.
- The RAR shows mild evolution with redshift in simulations.
- The gravitational field of the host galaxy does not influence the RAR of satellite galaxies within ΛCDM.
Conclusions:
- The observed scatter in dwarf spheroidal galaxies is consistent with ΛCDM predictions, suggesting they do not fundamentally deviate from the RAR.
- The absence of an external field effect in ΛCDM, contrasting with MOND, provides a potential method for discriminating between these cosmological models.
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