Constraining the role of radiative feedback processes during the formation of stars

Supervisors: Odysseas Dionatos and Manuel Güdel (Department of Astrophysics)

Funding Situation: potentially via a VISESS PhD fellowship

Project outline : Protostellar formation and growth occurs due to mass accumulation from a surrounding envelope onto a central source through the mediation of an accretion disk. Mass accretion is always followed by ejection of material forming collimated jets and wide-angle outflows, which remove the excess angular momentum from the system allowing further accretion  Propagating outwards, jets interact first with the dense envelope material leading to the formation of hollow cavities that appear to grow until the envelope is dispersed.  Within cavities, energetic radiation from the forming star can propagate and ionize the material along the cavity walls, accelerating the gradual erosion of the envelope and effectively reducing its mass. Feedback processes therefore regulate the final mass of forming stars, having a direct impact on the stellar initial mass function.

This study aims at constraining the role of energetic radiation in eroding and chemically altering the protostellar envelope material. The PhD project will develop a simple, mass-dependent evolution of the high-energy activity from the protostellar to the T Tauri phase. We will assemble datasets describing the SED for a sample of embedded (Class 0 and I) protostars and eruptive variables (FUORs and EXOrs); their properties will be estimated through comparisons with models of dust envelopes. Envelope masses and extinction will be then compared to X-ray data in order to constrain the net high-energy input into the system and compare it with more evolved, disk sources.