Detecting Adiabatic Contraction in Rotation Curves

TL;DR

This paper investigates how adiabatic contraction affects galaxy rotation curves, showing that contracted halos have distinct central profiles and that some galaxies, like NGC 6503, likely have minimally contracted halos based on rotation curve analysis.

Contribution

It provides a detailed analysis of adiabatic contraction effects on Einasto profiles and rotation curves, and assesses the contraction state of NGC 6503 using observational constraints.

Findings

Adiabatic contraction results in a central power index of ~0.7.

Contracted halos are well fit by double power laws beyond 1 kpc.

NGC 6503 likely has a minimally contracted halo.

Abstract

We examine the structure of adiabatically contracted Einasto profiles, using the prescriptions of Blumenthal et al. (1986) and Gnedin et al. (2004), and its impact on rotation curves. Adiabatically contracted halos display a central power index of ~0.7+/-0.1 for nearly all values of the Einasto shape parameter, alpha, and are well fit inside ~>1 kpc by double power laws. However, attempts to fit exponential disc and uncontracted halos to adiabatically contracted rotation curves yield disc masses and central power indices that are too large. We also determine whether or not the rotation curve of NGC 6503 displays evidence of adiabatic contraction using previously published bar formation constraints, and find that NGC 6503 most likely has a minimally contracted halo. However, this conclusion depends on the correct choice of circular velocity curve.