Baryonic solutions and challenges for cosmological models of dwarf galaxies

TL;DR

This paper reviews the challenges faced by the LCDM cosmological model in explaining dwarf galaxy observations and discusses how recent simulations incorporating baryonic physics offer potential solutions, while highlighting remaining tensions.

Contribution

It provides a comprehensive review of baryonic solutions to LCDM challenges in dwarf galaxies and identifies key unresolved issues needing further refinement.

Findings

Recent simulations suggest baryonic processes can resolve some LCDM discrepancies.

Remaining tensions include dark-matter content diversity and satellite plane alignments.

Refining galaxy formation models is crucial for resolving current challenges.

Abstract

Galaxies and their dark-matter halos have posed several challenges to the Dark Energy plus Cold Dark Matter (LCDM) cosmological model. These discrepancies between observations and theory intensify for the lowest-mass (`dwarf') galaxies. LCDM predictions for the number, spatial distribution, and internal structure of low-mass dark-matter halos have historically been at odds with observed dwarf galaxies, but this is partially expected, because many predictions modeled only the dark-matter component. Any robust LCDM prediction must include, hand-in-hand, a model for galaxy formation to understand how baryonic matter populates and affects dark-matter halos. In this article, we review the most notable challenges to LCDM regarding dwarf galaxies, and we discuss how recent cosmological numerical simulations have pinpointed baryonic solutions to these challenges. We identify remaining tensions, including the diversity of the inner dark-matter content, planes of satellites, stellar morphologies, and star-formation quenching. Their resolution, or validation as actual problems to LCDM, will likely require both refining galaxy formation models and improving numerical accuracy in simulations.