The puzzling assembly of the Milky Way halo - contributions from dwarf Spheroidals and globular clusters

TL;DR

This paper reviews the complex origins of the Milky Way halo, focusing on dwarf spheroidal galaxies and globular clusters, and discusses their roles in galaxy formation and the challenges in classifying these faint satellites.

Contribution

It provides a comprehensive overview of the stellar populations and chemo-dynamics of outer halo satellites, highlighting recent measurements and debates on their origins and classifications.

Findings

Outer halo objects may not be dynamically associated with the Milky Way.

Dwarf spheroidals and globular clusters have diverse chemo-dynamical properties.

Proper motion measurements are crucial for understanding halo assembly.

Abstract

While recent sky surveys have uncovered large numbers of ever fainter Milky Way satellites, their classification as star clusters, low-luminosity galaxies, or tidal overdensities remains often unclear. Likewise, their contributions to the build-up of the halo is yet debated. In this contribution we will discuss the current knowledge of the stellar populations and chemo-dynamics in these puzzling satellites, with a particular focus on dwarf spheroidal galaxies and the globular clusters in the outer Galactic halo. Also the question of whether some of the outermost halo objects are dynamically associated with the (Milky Way) halo at all is addressed in terms of proper measurements in the remote Leo I and II dwarf galaxies.