The link between disc dispersal by photoevaporation and the semi-major axis distribution of exoplanets

TL;DR

This study explores how photoevaporation of protoplanetary discs influences the final semi-major axis distribution of exoplanets, highlighting the importance of the photoevaporation model in shaping planetary orbits.

Contribution

It demonstrates that different photoevaporation models significantly affect the predicted exoplanet semi-major axis distribution, especially around 1-2 AU, aligning with observed features.

Findings

XEUV photoevaporation more effectively traps planets at 1-2 AU.

Final exoplanet distributions depend strongly on the photoevaporation model.

Caution is needed due to simplified planetary accretion modeling.

Abstract

We investigate the influence of photoevaporation of protoplanetary discs on the final distribution of exoplanets semi-major axis distances. We model giant planet migration in viscous discs affected by photoevaporation driven by either pure EUV or soft X-ray radiation (XEUV). We show that the final exoplanet distributions are strongly dependant on the choice of the photoevaporation model. In particular, we find that XEUV is more efficient than pure EUV radiation at parking planets at approximately 1-2 AU distance from their central star, hence roughly reproducing the observed peak in the exoplanets semi-major axis distributions. We note however that a more quantitative comparison with the observations is hindered by the oversimplified treatment of planetary accretion, which severely affects migration rates. For this reason, caution should be used when using these models to constrain details of disc clearing and/or migration from the observations. Nevertheless our results indicate that disc dispersal by photoevaporation may be the main driver of the features in the exoplanets semi-major axis distribution observed by recent surveys.