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Janez Kos: Recovering the history of the Milky Way through chemical tagging of stars and ultra-precise spectroscopy

Date: 22. 11. 2017
Source: Monday physics colloquium
Ponedeljek, 27. 11. 2017 ob 16.15 v predavalnici F1, UL FMF, Jadranska 19, Ljubljana

 

Recovering the history of the Milky Way through chemical tagging of stars and ultra-precise spectroscopy

 

Janez Kos

Sydney Institute for Astronomy, The University of Sydney

 

Galaxy formation and dynamical processes in the galaxies are best studied star-by-star, which is only possible in our own galaxy. Past events that shaped our Galaxy can only be studied via their remnants - stars that have since migrated all over the Galaxy. After a while, stars with a common past can only be identified via chemical signatures, as they have been born from the same material. Kinematic and spatial correlations disappear too fast. Therefore the aim of contemporary spectroscopic surveys of stars is to observe enough chemical elements to resolve individual ancient birthplaces of stars and recreate their migration paths. I will present the results of the largest such survey (GALAH) and the challenges we face to perform the precise measurements and find the chemical signatures in the big data. Measuring the abundances is a challenge that requires a good theoretical understanding of stellar atmospheres as well as very precise analysis of their spectra. We are developing unique procedures that phase out the traditional analysis of spectra. By precisely analyzing the optical transfer function of our instruments we can recreate the observations from theoretical models of stellar spectra and thus bypass all of the disadvantages of a traditional extraction of spectra from observed images.

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