Density profiles of dark matter haloes on Galactic and Cluster scales

TL;DR

This paper enhances the Extended Secondary Infall Model to better understand dark matter halo density profiles, showing how angular momentum and dynamical friction can flatten cusps on galactic scales and match observations.

Contribution

It introduces improvements to the ESIM by incorporating angular momentum, dynamical friction, and baryon effects, providing a more realistic model of dark matter halo profiles.

Findings

Angular momentum and dynamical friction can eliminate cusps on galactic scales.

The model fits observed rotation curves of LSB galaxies well.

Density profile slopes flatten to approximately 0 on galactic scales and 0.6 on cluster scales.

Abstract

In the present paper, we improve the "Extended Secondary Infall Model" (ESIM) of Williams et al. (2004) to obtain further insights on the cusp/core problem. The model takes into account the effect of ordered and random angular momentum, dynamical friction and baryon adiabatic contraction in order to obtain a secondary infall model more close to the collapse reality. The model is applied to structures on galactic scales (normal and dwarf spiral galaxies) and on cluster of galaxies scales. The results obtained suggest that angular momentum and dynamical friction are able, on galactic scales, to overcome the competing effect of adiabatic contraction eliminating the cusp. The NFW profile can be reobtained, in our model only if the system is constituted just by dark matter and the magnitude of angular momentum and dynamical friction are reduced with respect to the values predicted by the model itself. The rotation curves of four LSB galaxies from de Blok & Bosma (2002) are compared to the rotation curves obtained by the model in the present paper obtaining a good fit to the observational data. On scales smaller than $\simeq 10^{11} h^{-1} M_{\odot}$ the slope $\alpha \simeq 0$ and on cluster scales we observe a similar evolution of the dark matter density profile but in this case the density profile slope flattens to $\alpha \simeq 0.6$ for a cluster of $\simeq 10^{14} h^{-1} M_{\odot}$. The total mass profile, differently from that of dark matter, shows a central cusp well fitted by a NFW model.