Stellar cluster mergers and star formation in galactic nuclei

Nuclear star clusters (NSCs) are dense stellar systems known to exist in 
galactic nuclei. Although their evolution is connected to that of the host 
galaxy, their origin is still unknown. Two complementary formation channels have 
been proposed so far. In the first one, globular clusters (GCs) inspiral to the 
centre of the galaxy, merge and build up the NSC. In the second one, the NSC 
forms through episodic star formation events happening in central stellar discs, 
similar to the one observed at the Galactic Centre. 
In this seminar I will explore both these mechanisms. By using N-body 
simulations and models constrained by observations from the Milky Way, I will
illustrate how an NSC formed through the accumulation of GCs is characterised
by properties that make it comparable with the Galactic NSC. At the same time, 
our simulations show that star formation happening in gaseous discs orbiting 
the central supermassive black hole can reproduce the observed properties of 
multiple stellar populations in galactic nuclei differing in age, metallicity 
and kinematic properties.