Multidimensional hydrodynamical simulations of radiative cooling SNRs-clouds interactions: an application to starburst environments

¹ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil e-mail: [cmelioli;dalpino]@astro.iag.usp.br
² Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, 04510 México D.F., México

Received: 11 January 2005
Accepted: 18 July 2005

Abstract

Most galaxies present supernova shock fronts interacting with cloudy interstellar medium. These interactions can occur either at small scales, between a single supernova remnant (SNR) and a compact cloud, or at large scales, between a giant shell of a superbubble and a molecular cloud. Here study the by-products of SNR-clouds in a starburst (SB) system. Due to the high supernova (SN) rate in this environment, a cloud may be shocked more than once by SNRs. These interactions can have an important role in the recycling of matter from the clouds to the ISM and vice-versa. Their study is also relevant to understand the evolution of the ISM density and the structure of the clouds embedded in it.
In the present work, we have focused our attention on the global effects of the interactions between clouds and SN shock waves in the ISM of SB environments and performed three-dimensional radiative cooling hydrodynamical simulations which have included the continuity equations for several atomic/ionic and molecular species. We have also considered the effects of the photo-evaporation due to the presence of the UV radiation from hot stars and SNe. 
The results have shown that due to the presence of radiative cooling, the interactions cause the formation of elongated cold filaments, instead of favoring an efficient mixing of the cloud gas with the diffuse ISM. These filaments could be associated with the dense clumps observed inside several SBs that are blown out by the galactic wind. The results have also revealed that the SNR-cloud interactions are less efficient at producing substantial mass loss from the clouds to the diffuse ISM than mechanisms such as the photo-evaporation caused by the UV flux from the hot stars. This result has important consequences for the global evolution of the SB environment and the formation of the associated superwinds, and may also be relevant to the ISM of normal galaxies.