Ram pressure stripping of tilted galaxies

¹ Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 31 Prague 4, Czech Republic e-mail: jachym@ig.cas.cz, palous@ig.cas.cz
² Observatoire Astronomique de Strasbourg, 11 Rue de l'Université, 67000 Strasbourg, France e-mail: koppen@astro.u-strasbg.fr
³ International Space University, Parc d'Innovation, 1 Rue Jean-Dominique Cassini, 67400 Illkirch-Graffenstaden, France
⁴ Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany
⁵ Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France e-mail: francoise.combes@obspm.fr

Received: 4 December 2008
Accepted: 30 March 2009

Abstract

Context. Ram pressure stripping of galaxies in clusters can yield gas deficient disks. Previous numerical simulations based on various approaches suggested that, except for near edge-on disk orientations, the amount of stripping depends very little on the inclination angle.

Aims. Following our previous numerical and analytical study of face-on stripping, we extend the set of parameters with the disk tilt angle and explore in detail the effects of the ram pressure on the interstellar content (ISM) of tilted galaxies that orbit in various environments of clusters, with compact or extended distributions of the intra-cluster medium (ICM). We further study how results of numerical simulations could be estimated analytically. To isolate the effect of inclination, galaxies on strictly radial orbits are considered.

Methods. A grid of numerical simulations with varying parameters is produced using the tree/SPH code GADGET with a modified method for calculating the ISM-ICM interaction. These SPH calculations extend the set of existing results obtained from different codes using various numerical techniques.

Results. The simulations confirm the general trend of less stripping at orientations close to edge-on. The dependence on the disk tilt angle is more pronounced for compact ICM distributions, however it almost vanishes for strong ram pressure pulses. Although various hydrodynamical effects are present in the ISM-ICM interaction, the main quantitative stripping results appear to be roughly consistent with a simple scenario of momentum transfer from the encountered ICM. This behavior can also be found in previous simulations. To reproduce the numerical results we propose a fitting formula depending on the disk tilt angle and on the column density of the encountered ICM. Such a dependence is superior to that on the peak ram pressure used in previous simple estimates.