Title of the thesis
Stellar Streams for Galactic and Cosmic Archaeology : when gravity meets complexity
Composition of the jury
- Françoise Combes (Collège de France, Observatoire de Paris-PSL) Présidente du jury
- Jorge Peñarrubia (University of Edinburgh) - Rapporteur
- Anna Lisa Varri (University of Edinburgh) - Rapportrice
- Christian Boily (Université de Strasbourg ) - Examinateur
- Eugene Vasiliev (University of Surrey) - Examinateur
- Raffaella Schneider (Sapienza Università di Roma) - Examinatrice
- Paola Di Matteo (LIRA, Observatoire de Paris-PSL) - Superviser
- Marco Montuori (Istituto dei Sistemi Complessi, CNR, Roma) - Superviser
Summary
The Gaia astrometric mission has enabled large-scale studies of stars and Galactic substructures. About 160 Milky Way globular clusters (GCs), each with hundreds of thousands to millions of stars, can now be characterized via accurate distances, proper motions, radial velocities, masses, and sizes. Meanwhile, known stellar streams have grown from about 60 at the start of this thesis to over 120 today. Because streams trace progenitor orbits, they provide excellent probes of the Milky Way’s gravitational potential and dark matter perturbations. Enabled by this data, we studied the Galactic stellar stream and globular cluster system. I developed the open-source code tstrippy, which models tidal stripping of cluster stars via the restricted three-body problem. Using this framework, we predicted the distribution of tidal debris from all Galactic GCs and ran targeted simulations of Palomar 5’s stream, finding that “gaps” can be generated by GC flybys. We present the first global predictions of tidal debris from all Milky Way GCs. These simulations are publicly available and used by the community. In a follow-up study, we quantified the frequency and range of GC encounters perturbing Palomar 5, showing such interactions must be considered to avoid false positives in dark matter subhalo searches. We also showed that the presence, in a given region of the stellar stream, of populations of stars lost at different times can reduce gap persistence, lowering stream sensitivity to external perturbations. This work establishes the expected distribution of tidal streams from Galactic GCs and quantifies the rate at which GCs perturb Palomar 5. It provides a foundation for disentangling the origins of stream perturbations, studying the internal dynamics and evolution of globular clusters, and constraining the Milky Way’s gravitational potential in both visible and dark matter.
