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

Abstract

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.