Diverse Rotation Curves of Galaxies in a Simulated Universe: the Observed Dependence on Stellar Mass and Morphology Reproduced

TL;DR

This study uses the IllustrisTNG simulation to reproduce observed galaxy rotation curve diversity, showing dependence on stellar mass and morphology, and highlighting dark matter's role in shaping these curves.

Contribution

It demonstrates that cosmological simulations can replicate the observed dependence of rotation curves on galaxy properties, emphasizing dark matter's influence.

Findings

Outer rotation curve slopes vary with galaxy morphology and mass.

Simulated rotation curves correlate with dark matter fraction.

Diverse rotation curve patterns are successfully reproduced.

Abstract

We use the IllustrisTNG cosmological hydrodynamical simulation to study the rotation curves of galaxies in the local universe. To do that, we first select the galaxies with 9.4 $<$ $\log{(M_\mathrm{star}/M_\odot)}$ $<$ 11.5 to make a sample comparable to that of SDSS/MaNGA observations. We then construct the two-dimensional line-of-sight velocity map and conduct the fit to determine the rotational velocity and the slope of the rotation curve in the outer region ($R_\mathrm{t}<r<3\times r_\mathrm{half,*}$). The outer slopes of the simulated galaxies show diverse patterns that are dependent on morphology and stellar mass. The outer slope increases as galaxies are more disky, and decreases as galaxies are more massive, except for the very massive early-type galaxies. The outer slope of the rotation curves shows a correlation with the dark matter fraction, slightly better than for the gas mass fraction. Our study demonstrates that the observed dependence of galaxy rotation curves on morphology and stellar mass can be successfully reproduced in cosmological simulations, and provides a hint that dark matter plays an important role in shaping the rotation curve. The sample of simulated galaxies in this study could serve as an important testbed for the subsequent study tracing galaxies back in time, enabling a deeper understanding of the physical origin behind the diverse rotation curves.