The origin and assembly of star clusters: our Galactic building blocks
IDPASC Portugal - PHD Programme 2017
2017 / 2018
Faculdade de Ciências - Universidade de Lisboa
CENTRA / U. LIsboa
Stars form mainly in clustered mode. Over time, these clusters evaporate and/or disrupt, enriching the general field population. However, the question of the physical origin of stellar clusters remains largely a mystery. This is, in part, due to the fact that cluster formation is a complex physical process that is intimately linked to the process of star formation, for which there is as yet no complete theory. Open clusters are born in molecular clouds completely embedded in gas and dust, thus obscured from view at optical wavelengths. Fortunately, molecular clouds are considerably less opaque at infrared wavelengths. Now current state-of-the art infrared adaptive optics (AO) instruments at large telescopes, such as the VLT, can systematically study the extremely young embedded stellar clusters within nearby molecular clouds. This thesis project will concentrate on the characterization of a sample of 70 massive young stellar aggregates, both their stellar content as well as the properties of the clumps and the clouds on which the dense clump are embedded (distance, size, mass, structure). The sample has been obtained with the VLT-NACO camera and constitutes the largest AO survey on massive star forming regions, comprising about 70 of the most massive and youngest star formation regions in the Milky Way. While the stars within the clumps are not observabe at optical wavelengths, the star forming complexes to which they belong typically host populations of optically revealed stars, many of them expected to have parallax and proper motion measurements in the second data release of the ESA Gaia mission announced for April 2018. This will allow a 3D reconstruction of their local star forming interstellar medium thus providing a larger scale context to the embedded aggregates. The objectives of the study are to: - Carry a robust investigation on which stars form first: massive or non-massive? - Derive the observed properties of the clumps and clouds containing ongoing massive star formation. - Derive observed properties of the stellar content of these regions. - Characterise the the massive end of the Initial Mass Function (IMF). - Investigate primordial mass segregation.