On the influence of ram-pressure stripping on the star formation of simulated spiral galaxies

Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria e-mail: Thomas.Kronberger@uibk.ac.at

Received: 23 October 2007
Accepted: 24 January 2008

Abstract

Aims. We investigate the influence of ram-pressure stripping on the star formation and the mass distribution in simulated spiral galaxies. Special emphasis is put on the question of where the newly formed stars are located. The stripping radius from the simulation is compared to analytical estimates.

Methods. Disc galaxies are modelled in combined N-body/hydrodynamic simulations (GADGET-2) with prescriptions for cooling, star formation, stellar feedback, and galactic winds. These model galaxies move through a constant density and temperature gas, which has parameters comparable to the intra-cluster medium (ICM) in the outskirts of a galaxy cluster (T = 3 keV ≈ 3.6  10⁷ K and ρ  = 10^-28 g/cm³). With this numerical setup we analyse the influence of ram-pressure stripping on the star formation rate of the model galaxy.

Results. We find that the star formation rate is significantly enhanced by the ram-pressure effect (up to a factor of 3). Stars form in the compressed central region of the galaxy, as well as in the stripped gas behind the galaxy. Newly formed stars can be found up to hundred kpc behind the disc, forming structures with sizes of roughly 1 kpc in diameter and with masses of up to 10⁷ . As they do not possess a dark matter halo due to their formation history, we name them “stripped baryonic dwarf” galaxies. We also find that the analytical estimate for the stripping radius from a Gunn & Gott (1972) criterion agrees well with the numerical value from the simulation. Like in former investigations, edge-on systems lose less gas than face-on systems, and the resulting spatial distribution of the gas and the newly formed stars is different.