PhD course ACCRETION / EJECTION IN ASTROPHYSICS

Lecturers: D. Galli - F. Bacciotti

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This course provides a basic picture of how the processes of accretion and ejection of matter drive the formation of new stars, from their beginnings in the gravitational collapse of cold interstellar clouds to their emergence as young stars associated to powerful jets and planet-forming disks. 

The course is divided in two parts of 6 hr each.

The first part (3 lectures of 2 hr each, lecturer D. Galli) is focused on the inward accretion of mass induced by gravity and opposed by rotation and magnetic forces. After a general introduction on the cold phase of the interstellar medium, the basics of gravitational instability are reviewed, and the simplest models of spherical collapse analyzed in detail. Then the physics of accretion disks is presented, and the aspects relevant to planet formation are discussed.

The second part of the course (3 lectures of 2 hr each, lecturer F. Bacciotti) addresses the physical nature of protostellar jets and outflows, and their role in the angular momentum balance in the star formation process. After an overview on the observational characteristics, that testify the universality of the phenomenon, the mechanism of magneto-centrifugal acceleration is discussed in detail, with the aid of both analytical and numerical models. Then the course addresses the importance of spectral diagnostics techniques, that allow us to test the validity of the ideas proposed for the jet launch and role.