Astron. Astrophys. 364, 532-542 (2000)

The consequences of ram pressure stripping on the Virgo cluster spiral galaxy NGC 4522

B. Vollmer ^1,3, M. Marcelin ², P. Amram ², C. Balkowski ¹, V. Cayatte ¹ and O. Garrido <sup>2

1</sup> Observatoire de Paris, DAEC, UMR 8631, CNRS et Université Paris 7, 92195 Meudon Cedex, France
² Observatoire de Marseille, 2 Place le Verrier, 13248 Marseille Cedex 04, France
³ Institut für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstrasse 15, 69121 Heidelberg, Germany

Received 14 September 2000 / Accepted 11 October 2000

Abstract

New H Fabry-Perot interferometer observations of the Virgo cluster spiral galaxy NGC 4522 are presented. A velocity field up to a radius of 60" was obtained. The observed rotation curve is symmetric. It is not perturbed in the inner disk. For radii it shows a solid body rotation. We compare these data with a numerical model which includes the effects of ram pressure stripping. The model can reproduce the main characteristics of the H emission distribution and velocity field. We therefore conclude that the stripping event which caused the HI deficiency and the distorted H distribution and velocity field has been due to ram pressure. The closest passage of the galaxy to the cluster center is estimated to be 6.5 10⁸ yr ago. The observed recent star formation is due to the re-accretion of gas clouds which were accelerated to velocities below the escape velocity during the stripping event. Furthermore, the gas which is located at radii is part of an asymmetric expanding ring of gas clouds. A substantial part of these clouds is located above the disk plane. We predict the HI gas distribution and velocity field as it would be observed by deep 21 cm observations.

Key words: galaxies: individual: NGC 4522 galaxies: interactions galaxies: ISM galaxies: kinematics and dynamics

Send offprint requests to: B. Vollmer (Bernd.Vollmer@obspm.fr)

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Contents

• 1. Introduction
• 2. Observations and data reductions
  • 2.1. The GHASP survey
  • 2.2. Observations
  • 2.3. Reductions
• 3. The numerical model
• 4. Results
  • 4.1. The distribution of the ionized gas
  • 4.2. The velocity field of the ionized gas
  • 4.3. Off-plane material and predicted HI gas distribution and velocity field
• 5. Discussion and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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