Systematic effects on the diversity of dwarf galaxies rotation curves

TL;DR

This study shows that observational systematic effects like resolution and inclination can cause significant diversity in dwarf galaxy rotation curves, potentially explaining observed discrepancies without challenging the standard cosmological model.

Contribution

The paper demonstrates that modeling observational effects can account for a large portion of the rotation curve diversity seen in dwarf galaxies, reducing tension with simulations.

Findings

Systematic effects induce up to 47% of observed rotation curve diversity.

Resolution and inclination significantly impact rotation curve shapes.

Realistic modeling of observations can reconcile simulations with observations.

Abstract

Cosmological simulations of structure formation are invaluable to study the evolution of the Universe and the development of galaxies in it successfully reproducing many observations in the context of the cosmological paradigm $\Lambda$CDM. However, there are remarkable discrepancies with observations that are a matter of debate. One of the most recently reported is the diversity of shapes in the rotation curves of dwarf galaxies in the local Universe which is in contrast to the apparent homogeneity of rotation curves in cosmological hydrodynamic simulations. Previous studies on similar problems have shown that sometimes can be alleviated by accounting for the impact of observational effects in the comparison. For this reason, in this work we present a set of controlled experiments to measure the impact that some systematic effects, associated with modeling the observation process in a realistic way, have on the diversity of synthetic rotation curves. Our results demonstrate that factors such as spectral power, spatial resolution and inclination angle, can naturally induce noticeable fluctuations on the shape of the rotation curves, reproducing up to $47\%$ of the diversity reported in the observations. This is remarkable, especially considering that we limited the sample to highly-symmetric disks simulated in isolation. This shows that a more realistic modeling of synthetic rotation curves may alleviate the reported tension between simulations and observations, without posing a challenge to the standard cosmological model of cold dark matter.