The APOSTLE simulations: Rotation curves derived from synthetic 21-cm observations

TL;DR

This study uses the APOSTLE simulations to create synthetic 21-cm observations of dwarf galaxies, analyzing how non-circular motions affect the accuracy of derived rotation curves and dark matter inferences.

Contribution

It introduces a method to generate synthetic 21-cm observations from high-resolution cosmological simulations and assesses the impact of gas dynamics on rotation curve recovery.

Findings

Non-circular motions often hinder accurate rotation curve extraction.

Incorrect interpretation of dark matter distribution can result from gas dynamics.

Synthetic observations reveal potential biases in dark matter inferences.

Abstract

The APOSTLE cosmological hydrodynamical simulation suite is a collection of twelve regions $\sim 5$ Mpc in diameter, selected to resemble the Local Group of galaxies in terms of kinematics and environment, and re-simulated at high resolution (minimum gas particle mass of $10^4\,{\rm M}_\odot$) using the galaxy formation model and calibration developed for the EAGLE project. I select a sample of dwarf galaxies ($60 < V_{\rm max}/{\rm km}\,{\rm s}^{-1} < 120$) from these simulations and construct synthetic spatially- and spectrally-resolved observations of their 21-cm emission. Using the $^{3{\rm D}}$BAROLO tilted-ring modelling tool, I extract rotation curves from the synthetic data cubes. In many cases, non-circular motions present in the gas disc hinder the recovery of a rotation curve which accurately traces the underlying mass distribution; a large central deficit of dark matter, relative to the predictions of cold dark matter N-body simulations, may then be erroneously inferred.