A Virgo high-resolution Hα kinematical survey

I. NGC 4438

¹ Département de Physique, Université de Montréal, CP 6128, Succ. Centre-ville, Montréal, Qc, H3C 3J7, Canada e-mail: chemin@astro.umontreal.ca
² Observatoire de Paris, Section Meudon, GEPI, CNRS UMR 8111 & Université Paris 7, 5 Pl. Janssen, 92195 Meudon, France
³ Observatoire de Paris, Section Meudon, LUTH, CNRS-UMR 8102 & Université Paris 7, 5 Pl. Janssen, 92195 Meudon, France
⁴ Laboratoire d'Astrophysique de Marseille, 2 Pl. Le Verrier, 13248 Marseille, France
⁵ Laboratoire d'Astrophysique de Marseille, Traverse du Siphon-Les trois Lucs, 13012 Marseille, France

Received: 15 July 2004
Accepted: 28 February 2005

Abstract

New Hα emission-line observations of the Virgo cluster galaxy NGC 4438 are presented. Fabry-Perot interferometry data at an effective angular resolution of ~ are used to map the kinematics of the ionized gas in the galaxy. For the first time we obtain a velocity field covering a large area in NGC 4438, much larger than that deduced from previous Hi and CO maps. The kinematics of the extended, low surface brightness Hα filaments to the West of the galactic disk is discussed. We report on the discovery of a northern Hα structure which is clumpier than the other filaments. Evidence for multiple spectral components through the data-cube are presented in a nuclear shell and in the approaching half of the disk. The role of VCC 1040, a dwarf elliptical galaxy located to the South of NGC 4438, is presented to investigate the origin of a small-scale stellar tail of NGC 4438. It could be due to a minor tidal interaction between the two galaxies.