Cusp-core problem and strong gravitational lensing

TL;DR

This paper investigates whether baryon-cold dark matter interactions can universally resolve the cusp-core problem across different galaxy types by comparing rotation curve fits and strong lensing data.

Contribution

It demonstrates that the core sizes inferred from dwarf galaxy rotation curves cannot be applied to giant ellipticals, challenging the universality of baryon-dark matter interactions as a solution.

Findings

Core size from dwarf galaxies does not match that of giant ellipticals.

Baryon-dark matter interactions are not universal across galaxy types.

These interactions cannot fully solve the cusp-core problem in the standard cosmological model.

Abstract

Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation curves of cold dark matter-dominated dwarf and low surface brightness disk galaxies, with the latter tending to favor mass profiles with a flat central core. Many efforts have been devoted to resolve this cusp-core problem in recent years, among them, baryon-cold dark matter interactions are considered to be the main physical mechanisms erasing the cold dark matter (CDM) cusp into a flat core in the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are not customized only for CDM-dominated disk galaxies, but for all types, including giant ellipticals. We first fit the most recent high resolution observations of rotation curves with the Burkert profile, then use the constrained core size-halo mass relation to calculate the lensing frequency, and compare the predicted results with strong lensing observations. Unfortunately, it turns out that the core size constrained from rotation curves of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that, in the standard cosmological paradigm, baryon-cold dark matter interactions are not universal mechanisms for galaxy formation, and therefore, they cannot be true solutions to the cusp-core problem.