The metallicity distribution of the halo and the satellites of the Milky way in the hierarchical merging paradigm

TL;DR

This paper presents a semi-analytical model within the hierarchical merging framework to explain the metallicity distribution of the Milky Way halo and its satellites, accounting for observed features and discrepancies.

Contribution

It introduces a model that reproduces the halo's metallicity distribution and addresses the G-dwarf problem through early infall, linking halo formation to dwarf satellite accretion.

Findings

The model reproduces the shape and yield of the halo's metallicity distribution.

Early infall can explain the low-metallicity tail discrepancy.

Galactic halo likely formed from accreted dwarf-like galaxies.

Abstract

To account for the observed differential metallicity distribution (DMD) of the Milky Way halo, a semi-analytical model is presented in the framework of the hierarchical merging paradigm for structure formation. It is assumed that the Milky Way halo is composed of a number of sub-haloes with properties either as observed in the dwarf satellite galaxies of the Local group (shape of metallicity distribution, effective yield) or derived from calculations of structure formation (sub-halo distribution function). With reasonable assumptions for the parameters involved, we find that the overall shape and effective yield of the Galactic halo DMD can be reproduced in the framework of such a simple model. The low metallicity tail of the DMD presents a defficiency of stars with respect to the simple model predictions (akin to the G-dwarf problem in the solar neighborhood); it is suggested that an early infall phase can account for that problem, as well as for the observed DMDs of dwarf satellite galaxies.Accretion of galaxies similar (but not identical) to the progenitors of present day dwarf satellites of the Milky Way may well have formed the Galactic halo.