The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (bajtlik@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik.
Leda Berni (INAF- Osservatorio Astrofisico di Arcetri (Florence, Italy))
The Λ-CDM scenario predicts that the Milky Way assembled hierarchically, through the accretion of smaller systems such as globular clusters and dwarf galaxies. Although these systems can be disrupted by tidal interactions, their remnants survive as stellar streams that retain chemical and dynamical signatures of common origin. We developed CREEK, a machine-learning pipeline that learns similarity relations between stars using siamese neural networks, models their relational structure with graph neural networks autoencoders, and identifies substructures through density-based clustering (OPTICS). Applied to halo stars, our method recovers 80% of known globular clusters in the dataset, re-identifies established stellar streams, and reveals a candidate new substructure. We also detect two distinct populations within the Gaia Enceladus stream, possibly linked to multiple accretion passages through the Milky Way. The CREEK thus represents an objective and data-driven method for the selection of stars belonging to streams and to stellar structures in general, and the results highlight the capabilities of machine learning to find relations that would escape a classical search.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
Krzysztof Nalewajko (NCAC, Warsaw)
based on https://ui.adsabs.harvard.edu/abs/2025ApJ...995...26Z/abstract from Zhang et al. (2025)
