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 an exte nded pattern of strong star formation around one of its edges, which is pro bably due to some kind of interaction with the cluster environment. We pres ent Ha velocities within NGC 1427A, obtained through long-slit spectroscopy at seven different positions, chosen to fall on the brightest H rr regions of the galaxy. Because of its location very near the center of the cluster this object is an excellent candidate to study the effects that the cluste r environment has on gas-rich galaxies embedded in it. The rotation of NGC 1427A is modeled in two different ways. The global ionized gas kinematics i s reasonably well described by solid-body rotation, although on small scale s it shows a chaotic behavior. In this simple model, the collision with a s maller member of the cluster as being responsible for the peculiar morpholo gy of NGC 1427A is very unlikely, since the only candidate intruder falls s moothly into the general velocity pattern of the main galaxy. In a more ela borate model, for which we obtain a better solution, this object does not l ie in the same plane of NGC 1427A, in which case we identify it as a satell ite bound to the galaxy. These results are discussed in the context of a no rmal irregular versus one interacting with some external agent. Based on se veral arguments and quantitative estimates, we argue that the passage throu gh the hot intracluster gas of the Fornax Cluster is a very likely scenario to explain the morphological properties of NGC 1427A, although our kinemat ical data are not enough to support it more firmly nor rule out the possibi lity of a normal irregular.