SPH simulations of gas flow in barred galaxies. Effect of hydrodynamical and numerical parameters

We use SPH to calculate the gas response in a potential representing a stro ngly barred galaxy. We examine the dependence of the morphology and of the inflow rate of this response on hydrodynamical and numerical parameters use d in the simulations. In particular we study the effects of the sound speed , the rate of growth of the bar and the number of particles used in our mod els. We also investigate the appropriate value of the artificial viscosity to be used in the models, delimiting a region of values within which the fl ow is correctly described. We conclude that models with number of particles 10(4) < N less than or similar to 10(5) have similar overall morphology, a lthough their inflow rates may differ. The existence of straight-line "dust -lane" shocks is not affected by any of the above mentioned parameters. The y do, however, influence the location, the strength, the width and the long evity of these shocks. At sound speed c(8)=20 km s(-1) we find the longer l asting (for about 10 rotational periods of the bar) sharply described shock s. The "x(2)" region morphology changes slightly during the evolution of th e models. The sound speed influences both this rate of change and the inflo w rate of he gas. Finally introducing the bar abruptly from the beginning g ives a response morphology which is different from what is obtained if the bar is introduced slowly over two pattern rotations; this also influences t he inflow rate.