Old Globular Clusters in Dwarf Irregular Galaxies

Abstract

<p>One of the most pressing questions in astrophysics to date is resolving the history of galaxy assembly and their subsequent evolution. In the currently popular hierarchical merging” scenario, massive galaxies are believed to grow via numerous galaxy mergers. Present day dwarf irregular (dIrr) galaxies are widely regarded as the pristine analogs being the closest to resemble those pre-galactic building blocks. One way to approach this question is through studying the oldest stellar population in a given galaxy, and in particular the ancient globular star clusters whose properties unveil the conditions at the time of their early formation.<br /> To address the question of galaxy assembly the current work deals with studying the old globular clusters (GCs) in dIrr galaxies. By comparing the characteristics of GCs in massive galaxies an attempt is made to quantify the contribution of dIrr galaxies to the assembly of massive present-day galaxies and their globular cluster systems (GCSs). In particular, the Galactic GCS is known to harbor sub-populations of GCs whose properties (colors, luminosities, horizontal branch morphologies, structural parameters and orbital kinematics) suggest that they might have formed in low-mass satellites and were later incorporated into the Milky Way GCS.</p>