Spin alignment of stars in old open clusters

Titolo: Spin alignment of stars in old open clusters

Relatore: Enrico Corsaro (Marie Sklodowska-Curie Fellow AstroFIt2, Osservatorio Astrofisico di Catania)

Coordinate: mercoledì 15 marzo, ore 11, aula Ovest OACT

Abstract: Stars originate by the gravitational collapse of a turbulent molecular cloud of a diffuse medium, and are often observed to form clusters. Stellar clusters therefore play an important role in our understanding of star formation and of the dynamical processes at play. However, investigating the star formation is difficult because its physics is highly complex to be properly modeled, and because star forming regions are obscured by dust, which severely limits observations to infrared and radio bands only. As a consequence hierarchical-step approaches to decompose the problem into different stages are required, as well as reliable assumptions on the initial conditions in the clouds.

In this talk I will report for the first time the use of asteroseismology, namely the study of stellar oscillations, to put strong constraints on the early formation stages of open clusters, up to more than 8 billion years old. I will describe the analysis performed on a sample of 50 red giant stars in the old open clusters NGC 6791 and NGC 6819 observed by NASA Kepler, for which nearly 4000 oscillation modes have been fully characterized. I will therefore present the important discovery made about the rotation history of these clusters and how 3D hydrodynamical simulations for stellar cluster formation can be used to constrain the physical processes of turbulence and rotation that are in action during the proto-cluster formation. The results and implications of this work will be relevant for different fields in astrophysics, including planetary formation and galaxy formation, structure, and evolution. This research is being published in Nature Astronomy on March 13th 2017.