Project D
Exploring the Growth of Dense Stellar Systems Across Cosmic History
Martyna Chruslinska (ESO), Mirko Curti (ESO)
Stars exist in environments that differ by several orders of magnitude in the local density of stars and compact objects. Our Sun lives in the sparse galactic field, and it is extremely unlikely that it will ever be affected by a close flyby of another similarly massive object. On the contrary, such interactions are common in dense environments such as globular clusters or nuclear clusters. The latter are the densest stellar systems in the Universe, found at the centres of galaxies of all shapes and sizes. A fraction of their mass is thought to be made up of globular clusters that have spiralled into the central regions of galaxies. However, when and how these clusters accumulated their mass is still an open question. In recent years, dense environments have received particular attention in the field of gravitational wave astrophysics. Dynamical interactions in such environments can lead to the efficient formation of stellar black hole mergers (the main sources of gravitational waves observed by current detectors), possibly allowing hierarchical merging of black holes and even their growth into intermediate-mass black holes. How common are such processes in the Universe, and how likely are we to detect gravitational wave sources that have formed in this way?
The answer depends, among other things, on how much of the cosmic stellar mass is in dense environments and how this mass grows through cosmic history. During the project, we will follow the cosmic star formation history of different environments and explore different aspects of this problem using semi-analytical models and custom-made python scripts. Depending on your interest and time, you will have the opportunity to help develop the models, propose and test how different assumptions affect the buildup of dense environments and the gravitational-wave observable properties of black holes