11 papers
Time evolution of gaps in stellar streams in axisymmetric Stäckel potentials
Helmer H. Koppelman, Amina Helmi
When a subhalo interacts with a cold stellar stream it perturbs its otherwise nearly smooth distribution of stars, and this leads to the creation of a gap. The properties of such g…
Frequencies, chaos and resonances: a study of orbital parameters of nearby thick disc and halo stars
Helmer H. Koppelman, Jorrit H. J. Hagen, Amina Helmi
We study the distribution of nearby thick disc and halo stars in subspaces defined by their characteristic orbital parameters. Our aim is to establish the origin of the structure r…
Galactic potential constraints from clustering in action space of combined stellar stream data
Stella Reino, Elena M. Rossi, Robyn E. Sanderson +4
Stream stars removed by tides from their progenitor satellite galaxy or globular cluster act as a group of test particles on neighboring orbits, probing the gravitational field of…
A massive mess: When a large dwarf and a Milky Way-like galaxy merge
Helmer H. Koppelman, Roy O. Y. Bos, Amina Helmi
Circa 10 billion years ago the Milky Way merged with a massive satellite, Gaia-Enceladus. To gain insight into the properties of its debris we analyse in detail the suite of simula…
Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history
Helmer H. Koppelman, Amina Helmi, Davide Massari +2
Aims. Several kinematic and chemical substructures have been recently found amongst Milky Way halo stars with retrograde motions. It is currently unclear how these various structur…
Origin of the system of globular clusters in the Milky Way
Davide Massari, Helmer H. Koppelman, Amina Helmi
. The assembly history experienced by the Milky Way is currently being unveiled thanks to the data provided by the mission. It is likely that the globular cluster s…