On the complex stellar populations of ancient stellar systems
| PhD ceremony: | Mr A. (Alessandro) Savino |
| When: | November 02, 2018 |
| Start: | 14:30 |
| Supervisors: | prof. dr. E. (Eline) Tolstoy, prof. dr. M. Salaris |
| Where: | Academy building RUG |
| Faculty: | Science and Engineering |
Studying the ancient stars in present-day nearby galaxies, to reconstruct their past goes by the name of stellar archaeology. In recent years, precise observations revealed that many ancient stellar systems in the vicinity of the Milky Way are more complex than it was previously assumed. These complexities pose a challenge to the formation scenarios of stellar populations in the early Universe.
In my Ph.D. thesis, I present work that is aimed to characterize more precisely the properties of ancient stellar populations in nearby stellar systems. Most of my work focuses on the derivation of the rate at which galaxies formed new stars during their life. This quantity is called star formation history and it is derived by measuring the properties of galaxies’ hydrogen-burning stars, which are faint and difficult to observe. I investigate the use of helium-burning stars, much brighter, to refine the measurement of star formation histories and deliver a more detailed view of galaxy formation in ancient epochs. I also study M13, an old star cluster in our own galaxy, using data from a small ground-based telescope to trace chemical inhomogeneities in different regions of the cluster.
The tools that I developed and validated in this Ph.D. thesis will permit to extend our study of old stellar populations on a much larger number of stellar systems, refining our understanding of star formation in ancient times.