Protoplanetary discs in local star forming regions

Protoplanetary discs, the birthplaces of planets, can be influenced by the process of external photoevaporation. How do we expect this influence the properties of these discs?

How do discs survive in the Orion Nebula cluster?

The Orion Nebula cluster (ONC) is home to the classic 'proplyds' (strongly irradiated protoplanetary discs), which exhibit mass-loss rates of up to 0.1 solar masses per Myr. We would expect these discs to be destroyed quickly - and yet the majority of stars still host discs! This 'proplyd lifetime problem' has been a challenge for astronomy for about 25 years. In this paper we suggest a new solution to this problem. In this model, an extended period of star formation results in outward migration of older stars, and inward migration of young stars. The discs around the young stars are therefore those that are most strongly irradiated by the massive star, and their youth is what allows them to survive!

Discs in sigma Orionis

In some regions, we now see evidence of the influence of external photoevaporation on the dust content of the protoplanetary discs. Once such region is sigma Orionis, where dust mass is anti-correlated with distance to the 17 solar mass star, sigma Ori. We have demonstrated in our models that this depletion can be explained by external photoevaporation. In the below figure we show the observed dust masses as a function of stellar mass (left) and the model outcome (right). We find good agreement between the model and the observations, suggesting that external photoevaporation does play a role in this region. We also show that these discs may be used as a probe of angular momentum transport in discs... see the paper for more!

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