Self-consistent massive disks in triaxial dark matter halos

TL;DR

This paper develops a method to determine the equilibrium shape of galactic disks in triaxial dark matter halos, revealing that disks tend to circularize the potential at small radii, impacting galaxy rotation curve interpretations.

Contribution

It introduces a new technique that accounts for radial variations in halo potential and disk ellipticity, improving understanding of disk-halo interactions in triaxial halos.

Findings

Disks circularize the potential at small radii.

Model ellipticities match observational estimates.

Implications for dark matter halo density profiles.

Abstract

Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to calculate the equilibrium configuration of such a disk in the combined disk-halo potential, which is based on the method of Jog (2000) but accounts for the radial variation in both the halo potential and the disk ellipticity. This crucial ingredient results in qualitatively different behavior of the disk: the disk circularizes the potential at small radii, even for a reasonably low disk mass. This effect has important implications for proposals to reconcile cuspy halo density profiles with low surface brightness galaxy rotation curves using halo triaxiality. The disk ellipticities in our models are consistent with observational estimates based on two-dimensional velocity fields and isophotal axis ratios.