Astron. Astrophys. 349, 411-423 (1999)

Kinematics of the anemic cluster galaxy NGC 4548

Is stripping still active?

B. Vollmer ^1,3, V. Cayatte ³, A. Boselli  ^{*  4}, C. Balkowski ³ and W.J. Duschl <sup>1,2

1</sup> Institut für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstrasse 15, D-69121 Heidelberg, Germany
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
³ Observatoire de Paris, DAEC, UMR 8631, CNRS et Université Paris 7, F-92195 Meudon Cedex, France
⁴ Laboratoire d'Astronomie Spatiale du CNRS, B.P. 8, Traverse du Siphon, F-13376 Marseille Cedex 12, France

Received 29 April 1999 / Accepted 9 July 1999

Abstract

We present new HI (20" resolution) and CO observations of NGC 4548, an anemic galaxy in the Virgo cluster. The atomic gas distribution shows a ring structure which is distorted at the northern edge. The overall rotation curve is derived with a tilted ring model. We compare our rotation curve with previous ones and discuss the differences. The velocity field of the CO pointings fits very well with the one of the atomic gas where they overlap. The CO emission permits the extension of the rotation curve towards the galaxy centre. The molecular fraction is derived for the inner centered on the galaxy. We compare the HI and CO emission to H line and optical blue emission maps. The bar in the centre favors star formation at the outer end of the bar. The HI intensity distribution and velocity field of the northern perturbation are deprojected with the help of a first order kinematical model. They are discussed in the framework of warps. It is concluded that the scenario of ram pressure stripping responsible for the gas removal and the northern perturbation is a very probable one. In this case the ram pressure which may have caused the galaxy's HI deficiency is now fading after the galaxy's close passage to the cluster centre or increasing again due to a second approach of the galaxy to the cluster centre.

Key words: galaxies: individual: NGC 4548 galaxies: interactions galaxies: ISM galaxies: kinematics and dynamics

* Visiting Astronomer, Kitt Peak national Observatory, National Optical Astronomical Observatories.

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

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and data reduction
  • 2.1. The HI data
  • 2.2. The CO data
  • 2.3. The H data
  • 2.4. The optical data
• 3. Results
• 4. Kinematics
  • 4.1. The rotation curve
  • 4.2. A three dimensional method to visualize the HI data cube
  • 4.3. Adding the CO pointings to the cube
  • 4.4. First order modeling
• 5. Discussion
• 6. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999
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