Globular clusters and dwarf spheroidal galaxies of the outer galactic halo: On the putative scenario of their formation
According to observational data, some of the Galactic globular clusters (GCs) belonging to the outer halo form a separate subsystem of globulars: they are mainly on retrograde orbits, show younger ages than other GCs of the outer halo, etc. Moreover, there is evidence suggestive of a common, accretive origin of at least some of both these GCs and the dwarf spheroidal galaxies, satellites of the Milky Way. I discuss a scenario which, if real, would explain the origin and several peculiar characteristics of the objects under consideration. It is based on two fairly realistic assumptions: (i) the first burst of star formation in which a bulk of the population II formed in the Galaxy and M 31, led to a considerable mass loss, up to half mass of each protogalaxy; (ii) the Milky Way together with M 31 have formed a binary galactic system since the earliest epoch. Hence I suggest that just after (or during) the formation of their spheroids the Galaxy and M 31 mutually exchanged gas by its transfer, in particular, through respective Lagrangian point in approximately the same manner as in interacting binary star systems. So, some objects of the outer Galactic halo may have formed from gas produced in such a process.