Ram pressure stripping of the multiphase ISM and star formation in the Virgo spiral galaxy NGC 4330

¹ CDS, Observatoire astronomique de Strasbourg, UMR 7550, 11 rue de l’université, 67000 Strasbourg, France
e-mail: Bernd.Vollmer@astro.unistra.fr
² Astronomical Observatory, Jagiellonian University, Kraków, Poland
³ Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, OASU, CNRS/INSU, 33271 Floirac, France
⁴ Yale University Astronomy Department, PO Box 208101, New Haven, CT 06520-8101, USA
⁵ Max-Planck-Insitut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁶ Department of Astronomy and Space Science, Yonsei University, Republic of Korea
⁷ Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027, USA

Received: 11 July 2011
Accepted: 11 November 2011

Abstract

It has been shown that the Virgo spiral galaxy NGC 4330 shows signs of ongoing ram pressure stripping at multiple wavelengths. At the leading edge of the interaction, the Hα and dust extinction curve sharply out of the disk. On the trailing side, a long Hα/UV tail has been found which is located upwind of a long Hi tail. We complement the multiwavelength study with IRAM 30m HERA CO(2–1) and VLA 6 cm radio continuum observations of NGC 4330. The data are interpreted with the help of a dynamical model including ram pressure and, for the first time, star formation. Our best-fit model qualitatively reproduces the observed projected position, the radial velocity of the galaxy, the molecular and atomic gas distribution and velocity field, and the UV distribution in the region where a gas tail is present. However, the observed red UV color on the windward side is currently not reproduced by the model. On the basis of our model, the galaxy moves to the north and still approaches the cluster center with the closest approach occurring in  ~100 Myr. In contrast to other Virgo spiral galaxies affected by ram pressure stripping, NGC 4330 does not show an asymmetric ridge of polarized radio continuum emission. We suggest that this is due to the relatively slow compression of the ISM and the particular projection of NGC 4330. The observed offset between the Hi and UV tails is well-reproduced by our model. Since collapsing and starforming gas clouds decouple from the ram pressure wind, the UV-emitting young stars have the angular momentum of the gas at the time of their creation. On the other hand, the gas is constantly pushed by ram pressure. We provide stellar age distributions within three radial bins in the galactic disk (R > 5 kpc). Deep optical spectra could be used to test the quenching times suggested by our analysis. The reaction (phase change, star formation) of the multiphase ISM (molecular, atomic, ionized) to ram pressure is discussed in the framework of our dynamical model.