R. Capuzzo-Dolcetta

NLTE H2 Cooling Function and Protogalactic Evolution

We performed detailed NLTE calculation of the absorption (due to bound-bound transitions among the roto-vibrational levels of the molecule and due to scattering on bound electrons) and emission (due to the roto-vibrational transitions) functions of the H2 molecule in a low temperature and density gas typical of protogalactic conditions. All the details of the computations together with the presentation of fitting functions to the results, suitable to be used in heavy numerical codes which have the aim to follow the protogalaxy collapse, will be published elsewhere (Capuzzo-Dolcetta, Di Fazio and Palla, 1989); here we report the results and conclusions on H2 roto-vibrational cooling.

Turbulence in the Frame of the Evolution of a Self-Gravitating Protocloud

This paper studies the influence of turbulence generated by the supersonic motion of fragments formed during the collapse of a self-gravitating cloud. We investigate the dependence of the results upon the physical parameters, needed to describe turbulence. The results are given for three values of the gas cloud mass. The presence of turbulence with consequent dissipation is shown to raise appreciably the gas temperature. The results show that the turbulent velocity dispersion is sistematically smaller than the fragments’ orbital velocity dispersion.

A MultiFluid Hydrodynamical Radiative Model for the Evolution of a Spherical Protogalaxy

In this paper we present a new radiative, multifluid, hydrodynamical model of protogalactic evolution, using the fragmentation law by Di Fazio (1986). A treatment for radiation transport suitable for non-equi1ibrium conditions was included. The most important results are : strong shock waves are formed at the time of the bounce of the system, causing a mass loss from the protogalaxy both in fragments and gas; the initial quasi-isothermal phase at ≈ 300 °K is abruptly abandoned when the collapse heating overwhelms the molecular hydrogen radiative cooling, and the second quasi-isothermal phase at ≈ 3500 °K is also abandoned when the center of the system reaches a bremsstrahlung phase. The X-luminosity is, in this phase, similar to that of QSO’s. After this transient violent radiative phase, the protogalaxy’s radiation activity seems to slowly decline and degrade towards longer wavelengths. In the stellar mass range, two peaks are attained in the IMF at ≈ 20 and ≈ 100 M⊙. The slopes of the declining part of the IMF in that range is similar to Salpeter’s. Globular clusters seem to form in two bursts, in regions r > 7 Kpc and r > 20 Kpc. with radial metallicity distribution implications. The slope of the globular cluster family IMF is ≈ −1.8.