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The impact of environment on the evolution of protoplanetary discs: external photoevaporation and tidal encounters

Event Details

Event Dates: 

Friday, December 5, 2014 - 12:00pm

Seminar Location: 

  • CASA Conference Room C324

Speaker Name(s): 

Stefano Facchini

Speaker Affiliation(s): 

University of Cambridge
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

There is observational evidence that the environment of star forming regions can significantly affect the evolution of protostellar and protoplanetary discs. When stars form in groups, EUV (Extreme Ultraviolet) and FUV (Far Ultraviolet) radiation permeate the young association, interact with the gas of the disc, and can drive a gaseous flow from the disc’s edge. Whereas it is well known that strong FUV backgrounds drive vigorous photoevaporation (as in the Orion proplyds) it is usually assumed that the effect of the weak FUV background fields found in nearby star-forming regions have a negligible effect on disc evolution. We have built a new 1D model in order to find the radial steady-state structure of the gaseous wind flowing from accretion discs in both strong and weak FUV fields. Our results reveal that discs are subject to strong flows even in the presence of weak background fields (G0 ∼ 30 Draines) if they extend to radii > 100 AU. This implies a natural mechanism for limiting the radial spreading of protoplanetary discs, and therefore constrains the planet-formation potential in their outer regions (where most of the mass lies). This could be significant for the majority of planetary systems, since the threshold FUV field is so low. In cluster environments, the other fundamental phenomenon in the evolution of protoplanetary discs is tidal interactions. We will present a detailed model of the RW Aur system. By performing 3D hydro simulations and producing synthetic observations, we will show that this peculiar object is very likely undergoing a tidal encounter caused be the secondary star. RW Aur is the only known good candidate undergoing such mechanism on the scale of protoplanetary discs. It could thus be a key system to help constrain this important phenomenon.