Amina helmi thesis

For one of her projects, Helmi was involved in the design of Gaia, the newest satellite of the European Space Agency (ESA) that was launched in 2013. This satellite measures the location and motion of a billion stars in our Milky Way. By comparison: the ESA satellite Hipparcos, Gaia’s predecessor that provided Helmi with data for her promotion research in 1997, ‘only’ delivered information about a 100,000 stars and was far less accurate. No wonder that Helmi – together with the rest of the astronomy community – could not wait to see the first results in September 2016.

We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high latitude sky survey. Our sample contains 101 photometrically selected ... more abstract We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity and metallicity information. We have developed a new clustering estimator: the "4distance" measure, which when applied to our data set leads to the identification of 1 group and 7 pairs of clumped stars. The group, with 6 members, can confidently be matched to tidal debris of the Sagittarius dwarf galaxy. Two pairs match the properties of known Virgo structures. Using models of the disruption of Sagittarius in Galactic potentials with different degrees of dark halo flattening, we show that this favors a spherical or prolate halo shape, as demonstrated by Newberg et al. (2007) using SDSS data. One additional pair can be linked to older Sagittarius debris. We find that 20% of the star...

Amina helmi thesis

amina helmi thesis

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