20 May 2022Séminaire – Paolo Bianchini (ObAS)

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The renaissance of globular clusters: old stellar systems for new dynamical questions


The traditional picture of globular clusters (GCs) as old simple stellar systems is being radically revolutionized by groundbreaking observational programs such as Gaia and by extensive GPU-parallel N-body simulations. However, GC formation in the high-redshift universe still remains an open mystery of modern astrophysics. We now know that present-day Milky Way GCs display rich properties (e.g. internal rotation, tidal tails, complex stellar populations, stellar-mass black holes) and a fraction of them is expected to be the remnant of accreted dwarf galaxies, possibly still containing dark matter. 
In this talk, I will show how these rich dynamical properties offer the exciting possibility to unlock the mystery of GCs origin, while demanding at the same time for the development of a renewed and much more refined theoretical framework. First, I will highlight my effort in exploiting astrometric data to unveil the kinematic complexity in today’s GCs, both in their inner regions and in their outskirts. Subsequently, I will focus on the role of dynamical evolution driven by repeated star-by-star interactions (collisionality) which strongly reshapes GCs properties, such as their mass-to-light ratios. In particular, I will discuss how these complex dynamical effects can turn out to be extremely useful for the detection of stellar-mass and intermediate-mass black holes in GCs. Finally, I will introduce a new theoretical approach –the algorithm π-DOC– based on the combination of neural networks and N-body simulations, which aims at dramatically improving the measurement of GCs properties, explicitly taking into account their complex >10 Gyr dynamical evolution. Ultimately, this novel strategy, combined with state-of-the art data, will allow us to exploit GCs as probes of the high-redshift universe.