Probing Cosmology with ultra faint dwarf galaxies

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My research focuses on exploring one of the fundamental unknowns in physics and cosmology: mysterious "dark matter" which makes up 80% of the matter in the Universe. The nature of dark matter is not known but its evidence in galaxies and clusters of galaxies has been observed using its gravitational influence on the matter and light; e.g. affecting the motion of stars in galaxies.According to the current cosmological model, galaxies inhabit the centre of more extended dark matter halos. The dark matter halos of low mass galaxies (dwarf galaxies) and their fainter counterparts (ultra faint dwarfs or UFDs) are thought to be much more massive than the galaxies themselves. Dwarf galaxies and UFDs are therefore excellent laboratories to explore the properties of dark matter. Due to their low mass and faint nature, however, the study of these objects has been observationally and theoretically challenging. Most of the known UFDs have been discovered only in the very recent years, and theoretical understanding of, and predictions for, these objects are missing from the picture.During my fellowship, I develop and exploit extremely high resolution simulations of the formation and evolution of UFDs in their dark matter halos using a complex, state-of-the-art galaxy formation model. Such detailed and high resolution models of these extremely faint galaxies have not been possible up to this day.In my studies, I explore in detail the connection between UFDs and their dark matter halos using my simulations. I will address questions such as what is the dark matter content of UFD and how massive are their dark matter halos? What is the smallest halo that host UFDs? UFDs are amongst the first galaxies to form in the Universe after the Big Bang. I follow the formation of these objects in their dark matter halos and explore their different formation channels. Moreover, I study how these first galaxies affect their environment when the Universe was very young.Most of the currently known UFDs are located close to us, i.e. around our own galaxy, the Milky Way, and are satellites of the Milky Way. More of these extremely faint objects are expected to be discovered in the following years using up-coming telescopes, e.g. the Extremely Large Telescope. It is however not known how many more UFD are awaiting discovery. Using my research, I predict how many UFDs are expected to exist around the Milky Way and how they are distributed. My findings will guide the search for the missing dwarfs and UFDs in the up-coming years.In summary, I study the formation and evolution of ultra faint dwarf galaxies in a cosmological context in order to understand the connection between dark matter halos and galaxies at the faint end, and to provide predictions for the up-coming telescopes (e.g. the Extremely Large Telescope and the James Webb Space Telescope) which are expected to discover more of these galaxies in the nearby Universe, as well as early times.