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A&A 453, 883-893 (2006)
DOI: 10.1051/0004-6361:20064954
A dynamical model for the heavily ram pressure stripped Virgo spiral galaxy NGC 4522
B. Vollmer1, M. Soida2, K. Otmianowska-Mazur2, J. D. P. Kenney3, J. H. van Gorkom4 and R. Beck51 CDS, Observatoire astronomique de Strasbourg, 11 rue de l'université, 67000 Strasbourg, France
e-mail: bvollmer@astro.u-strasbg.fr
2 Astronomical Observatory, Jagiellonian University, Kraków, Poland
3 Yale University Astronomy Department, PO Box 208101, New Haven, CT 06520-8101, USA
4 Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027, USA
5 Max-Planck-Insitut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
(Received 2 February 2006 / Accepted 27 March 2006)
Abstract
Context.Recent HI and H
observations of NGC 4522 have revealed that this spiral galaxy represents
one of the best cases of ongoing ram pressure stripping in the Virgo cluster.
Aims.We determined the parameters of the interaction between the interstellar medium of
NGC 4522 and the intracluster medium of the Virgo cluster.
Methods.A dynamical model including ram pressure stripping is applied to the strongly HI deficient
Virgo spiral galaxy NGC 4522. A carefully chosen model snapshot is compared with existing
VLA HI observations.
Results.The model successfully reproduces the large-scale gas distribution and the velocity field. However it
fails to reproduce the large observed HI linewidths in the extraplanar component, for
which we give possible explanations. In a second step, we solve the induction equation on the
velocity fields of the dynamical model and calculate the large scale magnetic field. Assuming a
Gaussian distribution of relativistic electrons we obtain the distribution of polarized radio
continuum emission which is also compared with our VLA observations at 6 cm. The observed maximum
of the polarized radio continuum emission is successfully reproduced. Our model suggests that
the ram pressure maximum occurred only 
50 Myr ago.
Conclusions.Since NGC 4522 is
located far away from the cluster center (1 Mpc) where the intracluster medium density
is too low to cause the observed stripping if the intracluster medium is static and smooth,
two scenarios are envisaged: (i) the galaxy moves
very rapidly within the intracluster medium and is not even bound to the cluster;
in this case the galaxy has just passed the region of highest intracluster medium density;
(ii) the intracluster medium is not static but moving due to the infall of the M 49
group of galaxies. In this case the galaxy has just passed the
region of highest intracluster medium velocity.
This study shows the strength of combining high resolution HI and polarized radio continuum
emission with detailed numerical modeling of the evolution of the gas and the large-scale
magnetic field.
Key words: galaxies: individual: NGC 4522 -- galaxies: interactions -- galaxies: kinematics and dynamics -- galaxies: ISM
© ESO 2006