Star Cluster Formation and Galactic Assembly: from instrumentation, to observations and simulations

Globular clusters (GCs) lie at the intersection of many fields, serving as test beds for stellar evolution, dynamics, and chemical evolution and acting as tracers of Galactic evolution. Despite their prevalence across astrophysics, many fundamental questions remain. Specifically, how did GCs form and under what conditions? And how did they come to be in the MW today? In this thesis, we explore these questions by investigating GC formation, chemical and dynamical evolution, by attempting to use GCs as direct links to past MW merger events and by contributing to the next generation of instruments that study them. To explore GC formation, we perform a dynamical study of the remote halo GC, NGC 2419, to assess whether the cluster could have formed in a dark matter mini- halo. We use radial velocity observations and analytical as well as dedicated N-body models to investigate the effects of a halo. We also explore the chemical evolution of GCs by performing a high precision, differential abundance analysis of 15 red giant stars in the potential cluster siblings, NGC 288 and 362. Both clusters show sta- tistically significant dispersion in both iron and heavy elements, seemingly at odds with the current classifications of GCs. The dynamical evolution of GCs is probed via a theoretical study into the capabil- ities of the future ESO, ANU-led instrument, MAVIS. The MCAO-assisted Visible Imager and Spectrograph (MAVIS) will have the spatial resolution required to re- solve crowded GC centres and the astrometric accuracy to measure the motions of the central stars. To assess if this is feasible, we created the bespoke instrument simulator MAVISIM and showed that MAVIS could recover proper motion measure- ments sensitive enough to detect the presence of a 1500 solar mass black hole at a cluster centre. Finally, the connection between GCs and their host galaxies is tested chemo- dynamically by establishing chemical tags for accreted stars from the Gaia-Sausage- Enceladus (GSE) merger using high resolution spectroscopy. The two GCs, NGC 288 and NGC 362, dynamically associated with GSE, are compared with these tags to test chemical association. A galactic chemical evolution (GCE) model is built for GSE and fit to GSE stars and the two GCs. NGC 362 is found to have great chemi- cal similarity with GSE stars and is well-fit by the GCE model - suggesting a strong association with GSE. NGC 288 is not well fit by the GCE models - suggesting that the two GCs may not be associated with the same galaxy, or requiring GSE to have a certain level of chemical inhomogeneity.

Author dc:creator

• Monty, Stephanie

Language dc:language.iso

en_AU

Handle dc:identifier.uri

http://hdl.handle.net/1885/295594

OAI identifier oai:identifier

oai:openresearch-repository.anu.edu.au:1885/295594