Hidden treasures in Sagitarius

Hidden treasures in Sagitarius

When a young scientist is left free but protected to think, they can achieve amazing things. Sara Vitali has been exploring a galaxy hidden behind a huge interstellar gas cloud.

Leading a working group in Galactic astronomy is exciting because of the so many topics that Galactic astronomy encapsulates. We need to learn how to combine the physics of atomic nuclei with the properties of the interior and atmosphere of individual stars and the physics of large dynamical bodies like interacting galaxies. That really takes time! 

It is particularly challenging when several members in my team are working on these different topics, because as supervisor I have to change the mindset between a variety of problems while trying to keep the attention of every team member on the discussed topic. 

One tricky but very interesting project was brought to me by Sara Vitali. She applied to UDP when she was doing a master in Potsdam and was a member of the Pristine collaboration. I’ve been always interested about the work of that collaboration and Sara’s project on the analysis of the Sagittarius dwarf galaxy with Pristine metallicities was quite novel and unique.  I was very pleased when she accepted coming to work with me, and it’s been super fun to build the bridge between my research area with this particular project and collaboration. 

It seemed natural that Sara would spend the first period of her PhD writing up a paper of her master thesis results. Obviously the scientific interpretation of the metallicity distributions of this galaxy implied learning a lot about things I didn’t know! Sagittarius is a dwarf galaxy which is currently merging with the Milky Way, so its stellar populations are expected to be a total mess. Its core happens to be near the Galactic center, being super obscured by dust. This makes the stars, which are already very far away, extremely faint.

What are Sagitarius' stars made of? How is the evolutionary history of this galaxy and how is it driven by the different passages through our Milky Way?   As we discussed and studied the state-of-the-art of galaxy assembly and mergers, as well as the properties of dwarf galaxies for this paper, we’ve both become very fascinated about the prospects of using Pristine, Chilean observing facilities for spectroscopy, Gaia and the lessons learnt from the Millenium Nucleus ERIS to reconstruct histories with phylogenetic trees. It is such a cool PhD project! 

After an intense year of working from home while waiting for her visa to come to Chile, Sara arrived in Santiago just at the start of our winter to find herself struggling to get her residency papers done in a terribly unfriendly and badly working system. But she managed to do both, finish her first paper and pass her qualification exam.  Despite the difficulties in starting a PhD in such conditions, Sara smiles excited about keeping contributing to Galaxy evolution and making me learn every day something new about this intriguing patch of the sky. 

Paper link: ADS