The New Generation Planetary Population Synthesis (NGPPS)

III. Warm super-Earths and cold Jupiters: a weak occurrence correlation, but with a strong architecture-composition link

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: schlecker@mpia.de
² Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
³ Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA

Received: 1 June 2020
Accepted: 15 August 2020

Abstract

Context. Recent observational findings have suggested a positive correlation between the occurrence rates of inner super-Earths and outer giant planets. These results raise the question of whether this trend can be reproduced and explained by planet formation theory.

Aims. Here, we investigate the properties of inner super-Earths and outer giant planets that form according to a core accretion scenario. We study the mutual relations between these planet species in synthetic planetary systems and compare them to the observed exoplanet population.

Methods. We invoked the Generation 3 Bern model of planet formation and evolution to simulate 1000 multi-planet systems. We then confronted these synthetic systems with the observed sample, taking into account the detection bias that distorts the observed demographics.

Results. The formation of warm super-Earths and cold Jupiters in the same system is enhanced compared to the individual appearances, although it is weaker than what has been proposed through observations. We attribute the discrepancy to warm and dynamically active giant planets that frequently disrupt the inner systems, particularly in high-metallicity environments. In general, a joint occurrence of the two planet types requires intermediate solid reservoirs in the originating protoplanetary disk. Furthermore, we find differences in the volatile content of planets in different system architectures and predict that high-density super-Earths are more likely to host an outer giant. This correlation can be tested observationally.