Toward an initial mass function for giant planets

Daniel Carrera, Melvyn B. Davies, Anders Johansen
(Submitted on 25 Mar 2017)

The distribution of exoplanet masses is not primordial. After the initial stage of planet formation is complete, the gravitational interactions between planets can lead to the physical collision of two planets, or the ejection of one or more planets from the system. When this occurs, the remaining planets are typically left in more eccentric orbits. Here we use present-day eccentricities of the observed exoplanet population to reconstruct the initial mass function of exoplanets before the onset of dynamical instability. We developed a Bayesian framework that combines data from N-body simulations with present-day observations to compute a probability distribution for the planets that were ejected or collided in the past. Integrating across the exoplanet population, we obtained an estimate of the initial mass function of exoplanets. We find that the ejected planets are primarily sub-Saturn type planets. While the present-day distribution appears to be bimodal, with peaks around ∼1MJ and ∼20M⊕, this bimodality does not seem to be primordial. Instead, planets around ∼60M⊕ appear to be preferentially removed by dynamical instabilities. Attempts to reproduce exoplanet populations using population synthesis codes should be mindful of the fact that the present population has been depleted of intermediate-mass planets. Future work should explore how the system architecture and multiplicity might alter our results.

Comments:    10 pages, 9 figures; submitted to MNRAS
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1703.08647 [astro-ph.EP] (or arXiv:1703.08647v1 [astro-ph.EP] for this version)
Submission history
From: Daniel Carrera 
[v1] Sat, 25 Mar 2017 04:38:51 GMT (302kb,D)
https://arxiv.org/abs/1703.08647