Off-centering of the disk in the halo potential and the kinematic lopsidedness in the dwarf irregular galaxy WLM

Abstract

In this work, to investigate the dynamical nature of the kinematic asymmetry in the isolated gas-rich dwarf irregular galaxy W LM in the Local Group, we consider that the dark matter halo and the disk do not have the same center of mass (i.e., the disk lies off-center in the potential of the extended dark matter halo), which is one of the possible physical explanations for the kinematic lopsidedness. To do so, we generate a lopsided halo potential by considering two dark matter mass density models, ISO and Burkert, and we add up the contribution to the rotation curve of a perturbation term [Formula: see text] in the gravitational potential, which arises from the offset between the disk and the dark matter halo. We show that such an m = 1 perturbation improves the rotation curve modeling when compared to a non-perturbed potential and the shape of the HI gas rotation curves is fitted better in the approaching side if the perturbation term in the halo potential is taken into account for this galaxy dynamics. In fact, displacing the disk center by 0.1 kpc from the halo center is sufficient to provide such an improvement in modeling the rotation curve.