NGC 4254: a spiral galaxy entering the Virgo cluster

¹ CDS, Observatoire astronomique de Strasbourg, UMR 7550, 11 rue de l'Université, 67000 Strasbourg, France e-mail: bvollmer@astro.u-strasbg.fr
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ Observatoire de Paris, Section de Meudon, GEPI, CNRS UMR 8111 et Université de Paris 7, 5 place Jules Janssen, 92195 Meudon Cedex, France

Received: 25 May 2004
Accepted: 29 March 2005

Abstract

Deep Effelsberg Hi spectra of the one-armed, bright Virgo cluster spiral galaxy NGC 4254 are presented. Five different positions were observed in the 21 cm Hi line with the Effelsberg 100-m telescope: one in the center and 4 located one HPBW to the NE, NW, SW, and SE, respectively, from the galaxy center. The spectra are compared to existing deep VLA observations, and the single dish and interferometric Hi data are used to constrain a dynamical model which includes the effects of ram pressure. The peculiar, one-armed spiral pattern of NGC 4254 and its distorted and kinematically perturbed atomic gas distribution can be explained by a close and rapid encounter ~280 Myr ago with another massive Virgo galaxy, followed by ram pressure stripping that is ongoing. The stripping occurs almost face-on, since the angle between the disk and the orbital plane is . The galaxy with which NGC 4254 had its encounter is tentatively identified as the lenticular NGC 4262.