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

¹ Department of Astronomy, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
e-mail: tokyr@ast.uct.ac.za
² Observatoire d’Astrophysique de l’Université de Ouagadougou (ODAUO), BP 7021, Ouagadougou 03, Burkina Faso
³ LERMA, Observatoire de Paris, Collège de France, PSL, CNRS, Sorbonne Univ., UPMC, 75014 Paris, France
⁴ Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, ON K7K 7B4, Canada

Received: 9 June 2016
Accepted: 2 August 2016

Abstract

Context. We use Tree-SPH simulations from the GalMer database 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.

Aims. 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.

Methods. 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.

Results. Our results confirm that the tilted ring method implemented in ROTCUR systematically underestimates or 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 approximately ten degrees of the major or minor axis.