Evolution of stellar-gaseous disks in cosmological halos

¹ INAF-Osservatorio Astronomico di Torino. Strada Osservatorio 20, 10025 Pino Torinese (Torino), Italy e-mail: curir@oato.inaf.it
² INAF-Osservatorio Astronomico di Padova. Vicolo Osservatorio 5, 35122 Padova, Italy e-mail: paola.mazzei@oapd.inaf.it

Received: 27 March 2006
Accepted: 12 January 2007

Abstract

Aims.We explore the growth and evolution of the bar instability in stellar-gaseous disks embedded in a suitable dark matter halo evolving in a fully consistent cosmological framework. The aim of this paper is to point out the impact of different gas fractions on the bar formation, inside disks of different disk-to-halo mass ratio, and the role of the cosmological framework.

Methods.We performed cosmological simulations with the same disk-to-halo mass ratios as in a previous work where the gas was not taken into account. We compared results of the new simulations with the previous ones to investigate the effect of the gas by analysing the morphology of the stellar and gaseous components, the stellar bar strength, and the behaviour of its pattern speed.

Results.In our cosmological simulations, inside dark matter dominated disks, a stellar bar, lasting 10 Gyr, is still living at even if the gaseous fraction exceeds half of the disk mass. However, in the most massive disks we find a threshold value (0.2) of the gas fraction able to destroy the bar. The stellar bar strength is enhanced by the gas and in the more massive disks higher gas fractions increase the bar pattern speed.