Research project Multi-dimensional analysis of the metal-poor galaxy
The Milky Way is a puzzle made of hundreds of billions of individual pieces: a spectacular mixture of stars of all ages, some newly born and some as old as the Universe itself.
With data from telescopes on the ground and in space we determine the positions, motions, and chemical composition of millions of stars to reconstruct our Galaxy’s formation history and the origin of the elements.
Central to this ERC project are three optical multi-object spectrographs, each connected to a 4m-telescope: GALAH@AAT (Siding Spring Observatory, Australia), WEAVE@WHT (Roque de los Muchachos Observatory, La Palma, Spain) and 4MOST@VISTA (Paranal Observatory, Chile). Together, the surveys will collect tens of millions of stellar spectra.
Project description
The surfaces of stars like our Sun are boiling; surface convection cause enormous hot bubbles of gas to rise and overturn, releasing their surplus energy before the cooled gas trickles back to the deeper layers of the atmosphere. This phenomenon must be modelled by 3D radiation-hydrodynamic simulations running on supercomputers. We produce new models of metal-poor dwarf and giant stars, with upper surface layers that are significantly cooler than the traditional 1D hydrostatic models.
To accurately predict the strength of absorption lines in stellar spectra without resorting to the assumption of local thermodynamic equilibrium, we assemble new atomic models for iron-peak elements. The models contain information about their complex term structure and their radiative and collisional transition probabilities. Only a few years ago, such models contained very large uncertainties, due to the essentially unknown collisional cross-sections with neutral hydrogen, which is the main constituent of stellar atmospheres. Equipped with our new atomic models, we can investigate which violent stellar explosions created the Ti in your scissors or the Cu in your saucepan.
Stars have excellent memories; their chemical compositions always mirror their birth clouds and their orbital properties, like total energy and angular momentum, are preserved despite numerous laps around the centre of the Galaxy. We use clustering algorithms to search for over-densities in the multi-dimensional data sets that combine chemistry, motions, and age. Thereby, we identify remnants of very old clusters and dwarf galaxies scattered across the halo of the Milky Way, which helps us narrow down the sizes and timings of the giant engulfment events that produced them.
Project members
Project managers
Karin Lind
Associate Professor
Members
Karin Lind
Associate Professor
Cis Raf Lagae
PhD student
Jack William Edmund Mallinson
PhD student
Kristopher Charles Youakim
Researcher
Iryna Kushniruk
Postdoc
Mingjie Jian
postdoc, start oct 2022
Martin Montelius
Summer student 2021
Mila Racca
ERASMUS exchange student from Padova, 2022