Exploring the GalMer database: bar properties and non-circular motions

TL;DR

This study uses simulations from the GalMer database to analyze how bar structures in galaxies induce non-circular motions, affecting the accuracy of observed rotation curves and the methods used to derive galaxy properties.

Contribution

It compares intrinsic velocities from simulations with those obtained through observational algorithms, highlighting biases and limitations in current methods for analyzing barred galaxy kinematics.

Findings

The ROTCUR method underestimates or overestimates velocities by up to 40% in the inner galaxy regions.

DiskFit produces unrealistic results when the bar is near the galaxy's major or minor axis.

Simulations reveal significant biases in common observational techniques for barred galaxy rotation curves.

Abstract

We use Tree-SPH simulations from the GalMer database by Chilingarian et al. to characterize and quantify the non-circular motions induced by the presence of bar-like structures on the observed rotation curve of barred galaxies derived from empirical models of their line-of-sight velocity maps. The GalMer database consists of SPH simulations of galaxies spanning a wide range of morphological types and sizes. The aim is to compare the intrinsic velocities and bar properties from the simulations with those derived from pseudo-observations. This allows us to estimate the amount of non-circularity and to test the various methods used to derive the bar properties and rotation curves. The intrinsic velocities in the simulations are calculated from the gravitational forces whereas the observed rotation velocities are derived by applying the ROTCUR and DiskFit algorithms to well-resolved observations of intermediate-inclination, strongly barred galaxies. Our results confirm that the tilted ring method implemented in ROTCUR systematically underestimates/overestimates the rotational velocities by up to 40 percent in the inner part of the galaxy when the bar is aligned with one of the symmetry axes for all the models. For the DiskFit analysis, we find that it produces unrealistic values for all the models used in this work when the bar is within $\sim$10 degrees of the major or minor axis.