One of the most important puzzles in modern astrophysics is the nature of dark matter. Stellar streams, formed by tidal stripping of the stars from globular clusters or dwarf galaxies, behave as a... Show moreOne of the most important puzzles in modern astrophysics is the nature of dark matter. Stellar streams, formed by tidal stripping of the stars from globular clusters or dwarf galaxies, behave as a group of test particles allowing us to measure the Milky Way’s dark matter content and, therefore, offering us a key to understanding its nature. Open clusters, loosely bound groups of stars that move through the Galaxy together, are, in contrast, an important driver of stellar evolution research. This Thesis presents our studies of these Galactic substructures and the conclusions we can draw on the larger Universe and physics based on these local observations. In chapters 2 - 4, we apply a novel method to map the Milky Way’s dark matter content using stellar streams, taking care to understand the various possible contributors to the systematics. Chapter 5 is dedicated to the study of the Hyades open cluster. Show less
A century ago, it was unclear whether the stars in the sky were clustered in groups, or widely spread in the universe. Without accurate stellar distances, it was impossible to obtain a reliable... Show moreA century ago, it was unclear whether the stars in the sky were clustered in groups, or widely spread in the universe. Without accurate stellar distances, it was impossible to obtain a reliable spatial stellar distribution to know which stars are part of our Galaxy and those that were beyond. Recently, the Gaia mission provided accurate position and velocity measurements for a billion stars in the Milky Way. However, these measurements are limited by dust that absorbs and scatter the optical light, particularly forward the Galactic plane. In contrast, radio waves are not affected, and therefore, can easily penetrate the Galactic plane providing complementary data. Radio campaigns are currently measuring the positions and velocities of bright stellar sources in the Galactic plane using VLBI. This thesis demonstrates how accurate are these astrometric measurements for young massive and evolved stars. These results are (1) compared with simulations of unobserved Galactic areas to determine the structural parameters of the Galaxy, and (2) cross-matched between optical and infrared surveys to characterize different stellar populations. Finally, a study of a particular binary system was carried out that demonstrates the stellar information can be obtained by having accurate astrometry at different frequencies and epochs. Show less
