Kristopher Charles YouakimResearcher
About me
I have been a postdoctoral researcher in the astronomy department at Stockholm University since Nov 2020, after obtaining a PhD from Potsdam University in Germany.
My main field of research is galactic archaeology, which is the study of the formation and evolution of the Milky Way Galaxy using present day observations of stars. Our Galaxy has built-up over time by the merger of many smaller galaxies and clusters, who's stars get stripped and mixed into our Galaxy. The signatures of these past mergers are still visible today in the motions and chemical compositions of these stars. By studying the complex mixture of populations of stars in our Galaxy, we can look back in time to infer the conditions and environments in which these stars were born in the early Galaxy.
My current research interests include disentangling the accretion history of the Milky Way stellar halo, by using dynamical and chemical information of stars to associate them to their birth clusters and progenitor galaxies.
Research projects
Publications
A selection from Stockholm University publication database
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Tidal debris from Omega Centauri discovered with unsupervised machine learning
2023. Kris Youakim, Karin Lind, Iryna Kushniruk. Monthly notices of the Royal Astronomical Society 524 (2), 2630-2650
ArticleRead more about Tidal debris from Omega Centauri discovered with unsupervised machine learningThe gravitational interactions between the Milky Way and in-falling satellites offer a wealth of information about the formation and evolution of our Galaxy. In this paper, we explore the high-dimensionality of the GALAH DR3 plus Gaia eDR3 data set to identify new tidally stripped candidate stars of the nearby star cluster Omega Centauri (? Cen ). We investigate both the chemical and dynamical parameter space simultaneously, and identify cluster candidates that are spatially separated from the main cluster body, in regions where contamination by halo field stars is high. Most notably, we find candidates for ? Cen scattered in the halo extending to more than 50(?) away from the main body of the cluster. Using a grid of simulated streams generated with ? Cen-like orbital properties, we then compare the on sky distribution of these candidates to the models. The results suggest that if ? Cen had a similar initial mass as its present day mass, then we can place a lower limit on its time of accretion at t(acc) > 7 Gyr ago. Alternatively, if the initial stellar mass was significantly larger, as would be expected if ? Cen is the remnant core of a dwarf Galaxy, then we can constrain the accretion time to t(acc) > 4 Gyr ago. Taken together, these results are consistent with the scenario that ? Cen is the remnant core of a disrupted dwarf galaxy.
Show all publications by Kristopher Charles Youakim at Stockholm University