Seminar by Asier Lambarri on the topic of Star formation in the halo of the Vintergatan simulations

Seminar by Asier Lambarri, from the Universidad Complutense de Madrid, on the topic of star formation in the halo of the Vintergatan simulations.

Title: In situ stellar halo substructures in the Vintergatan Simulations

Abstract: Stellar haloes of massive galaxies and the substructures they contain are typically old, akin to the long timescales of merging processes in comparison to star-formation, quenching and stellar evolution timescales. There exists, however, an instance of a blue stream around NGC 7241 which, given the relatively low statistics in LSB observations and the typical 29 mag/arcsec² reached by current surveys, _ the question of how likely these structures may be in Milky-Way like haloes. The presence of blue substructures in the halo thus should mean in-situ star formation. In this work, we aim to provide a prediction of how likely these structures are using the Vintergatan simulations. We consider the formation of these structures through stripping of stars in infalling galaxies, inspired by one of the possible explanations for the blue stream, and through star-formation of CGM gas, either coming from the IGM or accreted satellites. We find a total of 24 candidates between the last major merger and current time, with preliminary analysis showing the most massive ones should be detectable by ARRAKIHS as blue-LSBF a few hundred Myr after the initial starburst. Three of such structures emerge from perturbations of cold streams of gas in the outer parts of the galactic halo. Although the low number of simulated galaxies prohibits drawing any statistically significant conclusions regarding the Vintergatan numerical model, this pilot study serves to show that such blue structures are able to form in high-res zoom-in simulations.