http://arxiv.org/abs/2107.02928
WLM is a dwarf irregular that is seen almost edge$-$on, which has prompted many kinematical studies to investigate its rotation curve and its dark matter content. In this paper, we investigate the origin of the strong asymmetry of the rotation curve, which shows a significant discrepancy between the approaching and the receding side. We first examine whether an $m = 1$ perturbation (lopsidedness) in the halo potential could be a mechanism creating such kinematical asymmetry. To do so, we fit a theoretical rotational velocity associated with an $m = 1$ perturbation in the halo potential model to the observed data via a $\chi-$squared minimization method. We show that a lopsided halo potential model can explain the asymmetry in the kinematic data reasonably well. We then verify that the kinematical classification of WLM shows that its velocity field is significantly perturbed, because of both its asymmetrical rotation curve and also because of its peculiar velocity dispersion map. Also based on kinemetry analysis, it is possible that WLM lies in the transition region, in which disk and merger coexist. In conclusion, it appears that the rotation curve of WLM diverges significantly from that of an ideal rotating disk, which may significantly affect investigations of its dark matter content.
M. Khademi, Y. Yang, F. Hammer, et. al.
Thu, 8 Jul 21
11/52
Comments: 12 pages, 6 figures, accepted for publication in Astronomy and Astrophysics (A & A)
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