The Ionized Gas Kinematics of the LMC‐Type Galaxy NGC 1427A in the Fornax Cluster

NGC 1427A is a LMC-like irregular galaxy in the Fornax cluster with anextended pattern of strong star formation around one of its edges, which isprobably due to some kind of interaction with the cluster environment. Wepresent H-alpha velocities within NGC 1427A, obtained through long-slitspectroscopy at seven different positions, chosen to fall on the brightest HIIregions of the galaxy. Due to its location very near the center of the clusterthis object is an excellent candidate to study the effects that the clusterenvironment has on gas-rich galaxies embedded in it. The rotation of NGC 1427Ais modeled in two different ways. The global ionized gas kinematics isreasonably well described by solid-body rotation, although on small scales itshows a chaotic behaviour. In this simple model, the collision with a smallermember of the cluster as being responsible for the peculiar morphology of NGC1427A is very unlikely, since the only candidate intruder falls smoothly intothe general velocity pattern of the main galaxy. In a more elaborate model, forwhich we obtain a better solution, this object does not lie in the same planeof NGC 1427A, in which case we identify it as a satellite bound to the galaxy.These results are discussed in the context of a normal irregular versus oneinteracting with some external agent. Based on several arguments andquantitative estimates, we argue that the passage through the hot intraclustergas of the Fornax cluster is a very likely scenario to explain themorphological properties of NGC 1427A.Comment: 31 pages, LaTeX2e, uses aas2pp4.sty and psfig.sty, including 7 Postscript figures; accepted for publication in ApJ, Vol. 530, February 200