The G-dwarf problem in the Galactic spheroid

摘要: Abstract This paper has two parts: one about observational constraints, and the other chemical evolution models. In first part, empirical differential metallicity distribution (EDMD) is deduced from different samples involving (i) 268 K-giant bulge stars [Sadler, E.M., Rich, R.M., Terndrup, D.M., 1996. AJ 112, 171], (ii) 149 globular clusters [Mackey, A.D., van den Bergh, S., 2005. MNRAS 360, 631], in addition to previous results (Caimmi, R., 2001b, AN 322, 241 (C01)) related (iii) 372 solar neighbourhood halo subdwarfs [Ryan, S.G., Norris, J.E., 1991. 101, 1865]. Under assumption that each typical for corresponding subsystem, EDMD of Galactic spheroid determined by weighting mass. The age-metallicity relation (EAMR) absolute ages recent a homogeneous sample [De Angeli, F., Piotto, G., Cassisi, et al., 130, 116]. second models are computed, assuming instantaneous recycling approximation. data fitted, an acceptable extent, simple implying both inhomogeneous star formation, provided formation inhibited during enhanced with respect disk neighbourhood, taken be representative whole disk. initial mass function (IMF) assumed universal power law, which implies same value true yield subsystems. theoretical (TDMD) separately, then EAMR cannot fitted into Simple model but shows non-monotonic trend characterized large dispersion. On hand, (TAMR) reproduces extent. For gas ouflow proto-halo, give rise predictions alternatives. If underwent decoupled evolution, i.e. no exchange between reservoirs, less than third outflowed proto-halo. coupled some existence unseen baryonic (or equivalent amount lost Galaxy) comparable mass, necessarily needed. this view, outflowing proto-halo remains bound Galaxy, produces