Adaptive Mesh Refinement Simulations of Galaxy Formation: Exploring Numerical and Physical Parameters

TL;DR

This study uses adaptive mesh refinement simulations to explore galaxy formation, focusing on how different physical and numerical parameters affect the development of disk galaxies and their rotation curves.

Contribution

It systematically investigates the impact of various simulation parameters, especially cooling suppression and feedback, on galaxy morphology and rotation curves in cosmological simulations.

Findings

Cooling suppression and feedback reduce the central peak of rotation curves.

Most parameters tested do not significantly alter the spheroidal component.

Standard models without feedback produce centrally peaked rotation curves.

Abstract

We carry out adaptive mesh refinement (AMR) cosmological simulations of Milky-Way mass halos in order to investigate the formation of disk-like galaxies in a {\Lambda}-dominated Cold Dark Matter model. We evolve a suite of five halos to z = 0 and find gaseous-disk formation in all; however, in agreement with previous SPH simulations (that did not include a subgrid feedback model), the rotation curves of all halos are centrally peaked due to a massive spheroidal component. Our standard model includes radiative cooling and star formation, but no feedback. We further investigate this angular momentum problem by systematically modifying various simulation parameters including: (i) spatial resolution, ranging from 1700 to 212 pc; (ii) an additional pressure component to ensure that the Jeans length is always resolved; (iii) low star formation efficiency, going down to 0.1%; (iv) fixed physical resolution as opposed to comoving resolution; (v) a supernova feedback model which injects thermal energy to the local cell; and (vi) a subgrid feedback model which suppresses cooling in the immediate vicinity of a star formation event. Of all of these, we find that only the last (cooling suppression) has any impact on the massive spheroidal component. In particular, a simulation with cooling suppression and feedback results in a rotation curve that, while still peaked, is considerably reduced from our standard runs.