Cosmology: small scale issues

TL;DR

This paper reviews small-scale challenges to the standard LambdaCDM model of galaxy formation, discussing issues like satellite abundance and density cusps, and considers implications for warm dark matter variants.

Contribution

It provides a comprehensive review of small-scale problems in LambdaCDM and explores how warm dark matter models might address these issues.

Findings

Current evidence is consistent with LambdaCDM

Data may favor a tepid version of warm dark matter

Very warm dark matter is constrained by observations

Abstract

The abundance of dark matter satellites and subhalos, the existence of density cusps at the centers of dark matter halos, and problems producing realistic disk galaxies in simulations are issues that have raised concerns about the viability of the standard cold dark matter (LambdaCDM) scenario for galaxy formation. This talk reviews these issues, and considers the implications for cold vs. various varieties of warm dark matter (WDM). The current evidence appears to be consistent with standard LambdaCDM, although improving data may point toward a rather tepid version of LambdaWDM - tepid since the dark matter cannot be very warm without violating observational constraints.