30.10.17 - An international team of astronomers, which includes the Laboratory of astrophysics of EPFL, has found evidence for the outer halo of our Galaxy to contain stellar debris of massive dwarf galaxies.

In the Lambda CDM paradigm, galaxies form hierarchically, starting from small stellar systems. However it is still to be unveiled what exactly our Galaxy was made of and the mass distribution of its building blocks. So far, most of the information we have on the Milky Way stellar halo comes from its inner part, the closest to the solar Neighborhood. For the first time, a sample of 28 stars were assembled to probe the chemical properties of distant regions in the outer halo with high resolution spectroscopic analysis in the optical. The abundances of a wealth of chemical elements have been derived. They have revealed clear signatures of extended star formation histories as seen only in the most massive dwarf galaxies of the Local Group.

Battaglia, G.; North, P.; Jablonka, P.; Shetrone, M.; Minniti, D.; Díaz, M.; Starkenburg, E.; Savoy, M.
What is the Milky Way outer halo made of ? High resolution spectroscopy of distant red giants.

Astronomy & Astrophysics, in press

Source:Laboratory of Astrophysics