Globular clusters (GCs) are the oldest stellar systems in the Galaxy and can be regarded as fossils from the violent epoch of Galaxy formation. The lifetimes of their very low mass main sequence stars (VLMMSSs) and brown dwarfs (BDs) are much longer than the age of the Galaxy, and thus samples of the VLMMSSs and BDs in GCs can provide us with important insights into the earliest stages of star formation in the Galaxy. Moreover, BDs represent a link between the lowest mass stars and giant planets, and thus are important for our understanding of stellar structure and evolution as well as star and planet formation. However, despite their importance for a range of astrophysical fields, our knowledge about old, metal-poor VLMMSSs and BDs is very limited. In fact, not a single BD has so far been detected in any GC. One goal of this project is to remedy this situation.
GCs are also highly dynamic systems. Indeed, the high stellar densities in their cores boost the formation of exotic populations like Blue Stragglers (BSs) which seem to be present in essentially all GCs. BSs are thought to be the merger product of two or more MS stars. They might have formed dynamically via direct collisions, or from binary evolution. As such, BSs can be seen as a dynamical signature of the present day GC, whereas VLMMSSs and BDs can be regarded as a signature of the early GC at the time of formation.
In this project, I will concentrate on both areas of GC research: the faint-end of the MS into the BD regime on one hand, and the cluster BSs on the other hand. Only such a combination, i.e the study of both VLMMSSs, BDs and BSs can provide insight in the dynamical evolution of the GCs as a whole; and test, for the first time, theoretical predictions that regard BDs on one side as the collisional relics of the parent cluster when it formed, and thus a dynamical signature of the early GC, and BSs on the other side as products of more recent collisional phenomena in the evolved, present day GC.
Fields of science
Call for proposal
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