Galactic wind in a starburst galaxy. The figure shows a snapshot
of a dense cold cloud overrun by a hot galactic wind. The simulation
takes into account radiative losses and heat conduction. The top panels
show the gas density (left) and pressure (right). The bottom panels
show the X-ray (left) and OVI (right) emissivity. The physical
dimension of each panel is 
pc
. The radius of the
initially spherical cloud is 10 pc.
People involved at OAB:
A. D'Ercole, in collaboration with F. Matteucci (Trieste Univ.), S. Recchi (University of Kiel) and M. Tosi continued the studies about the effects of SN explosions in starburst galaxies. The 2D simulations performed in the past (which take into account two different istantaneous bursts) are able to describe the general chemical and dynamical characteristics of the starburst galaxy IZw18. However, an analysis of the stellar population indicates that the first star burst must be continuous over a time span of several hundreds Myr. We thus introduced the possibility of continuous activity in our code. Under a number of simplyfing assumptions (centrally concentrated star formation and constant chemical composition of the newly formed stars) it was possible to study the dynamical and chemical effects of two star bursts extended in time and separated by a quiescent period, adopting the parameters suggested by Aloisi, Tosi & Greggio (1999). Contrary to models with instantaneous bursts, the present models are more stable and match the observed abundance ratio over longer time spans.
In collaboration with A. Marcolini and F. Brighenti (University of Bologna), D'Ercole extended to 3D a previously developed 2D hydrocode and studied the effect of the ram pressure of the IGM on dwarf galaxies and on galactic winds generated by starbursts occurring in these galaxies. A number of models have been run, covering different values of galactic mass, IGM ram pressure and inclination angle between the galactic rotation axis and the galactic velocity. While galactic winds in galaxies at rest carry away almost all the freshly produced metals, for particular combinations of the parameters the ram pressure may increase the fraction of metals which remain trapped into the ISM.
Finally, in collaboration with A. Marcolini and D. Strickland (Johns Hopkins University, Baltimore) D'Ercole started 2D simulations of cold clouds overrun by a hot galactic wind taking into account the heat conduction. The aim of these simulations is to explain the spatial distribution of the X-ray and OVI emissivity observed in starburst galaxies.
R. Bedogni has computed numerical simulations of SN remnant evolution in a cloudy medium for both Type I and Type II Supernovae. Particular attention has been paid to the evolution of the Rayleigh-Taylor instabilities inside the remnants because of the effects of cooling. More detailed simulations are done for the shock-clouds interactions for a wide range of the density contrast between the cloud and the ambient medium.
R. Bedogni, in collaboration with A. Di Fazio, (INAF-Rome Obs.), introduced the effects of a variable drag, in function of the Mach and Reynold numbers, in a more general program to obtain the dynamical evolution of a self-gravitating protocloud with turbulence. The fragmentation of a protocloud has been described using a ``semi-empirical" model of turbulence.
P. Londrillo has devised a new general method (Upwind Constrained Transport, UCT) to design higher order Godunov-type schemes for magneto-hydrodynamics (in collaboration with L. Del Zanna).
P. Londrillo, in collaboration with L. Ciotti (Astr. Dept., University of Bologna) and G. Bertin (University of Milano), has performed numerical and analytical analyses of a class of toroidal equilibria having relevance for stellar systems. Preliminary results have been presented at the AICPS Conference (Como, 2003).