Halo expansion in cosmological hydro simulations: towards a baryonic solution of the cusp/core problem in massive spirals

TL;DR

High-resolution cosmological hydrodynamical simulations including stellar feedback demonstrate that baryonic processes can transform cuspy dark matter profiles into cores in massive spiral galaxies, aligning models with observations.

Contribution

This study shows that baryonic feedback can create cored dark matter profiles in massive spirals, offering a baryonic solution to the cusp/core problem.

Findings

Dark matter cusps are transformed into cores by baryonic feedback.

Simulations produce flat rotation curves consistent with observations.

Extended stellar disks are formed, resembling real spiral galaxies.

Abstract

A clear prediction of the Cold Dark Matter model is the existence of cuspy dark matter halo density profiles on all mass scales. This is not in agreement with the observed rotation curves of spiral galaxies, challenging on small scales the otherwise successful CDM paradigm. In this work we employ high resolution cosmological hydro-dynamical simulations to study the effects of dissipative processes on the inner distribution of dark matter in Milky-Way like objects (M~1e12 Msun). Our simulations include supernova feedback, and the effects of the radiation pressure of massive stars before they explode as supernovae. The increased stellar feedback results in the expansion of the dark matter halo instead of contraction with respect to N-body simulations. Baryons are able to erase the dark matter cuspy distribution creating a flat, cored, dark matter density profile in the central several kpc of a massive Milky-Way like halo. The profile is well fit by a Burkert profile, with fitting parameters consistent with the observations. In addition, we obtain flat rotation curves as well as extended, exponential stellar disk profiles. While the stellar disk we obtain is still partially too thick to resemble the MW thin disk, this pilot study shows that there is enough energy available in the baryonic component to alter the dark matter distribution even in massive disc galaxies, providing a possible solution to the long standing problem of cusps vs. cores.