Modelling the Milky Way's exoplanet population based on cosmological galaxy simulations

TL;DR

This study combines cosmological galaxy simulations with exoplanet formation models to generate realistic exoplanet populations across the Milky Way, comparing results with observations and exploring variations in different galactic regions.

Contribution

It introduces a novel framework that integrates galaxy simulations with exoplanet models to predict exoplanet distributions in the Milky Way.

Findings

Simulated exoplanet distributions match Kepler observations after accounting for selection effects.

Most exoplanets in the solar neighborhood are Earth-like or super-Earths/Neptunes.

Differences in host star types and planet distributions highlight simulation limitations.

Abstract

In this paper we aim to simulate realistic exoplanet populations across different regions of the MW by combining state-of-the-art cosmological simulations of our Galaxy with exoplanet formation models and observations. We model the exoplanet populations around single stars, using planet occurrence rates and multiplicity depending on stellar mass, metallicity, and planet type, and assign them physical parameters such as mass and orbital period. Focussing first on the solar vicinity, we find mostly metallicity-driven differences in the distributions of non-hosting and planet-hosting single stars. In our simulated solar neighbourhood, 52.5% of all planets are Earth-like (23% of them located in the Habitable Zone), 44% are super-Earths/Neptunes, and 3.5% are giant planets. A comparison with the census of Kepler exoplanets and candidates shows that, when taking into account the most relevant selection effects, we obtain a similar distribution of exoplanets compared to the observed population. However, we also detect significant differences in the exoplanet and host star distributions (e.g. more planets around F-type and red-giant stars compared to observations) that we attribute mostly to a too strong recent star formation and a too large disc scale height in the simulation, as well as to some caveats in our exoplanet population synthesis that will be addressed in future work. Extending our analysis to other regions of the simulated MW and to other simulated galaxies, we find that the relative percentages of planet types remain largely consistent as long as the simulated galaxy matches the morphology and mass of the MW. We have created a fast and flexible framework to produce exoplanet populations based on MW-like simulations that can easily be adapted to produce predictions for the yields of future exoplanet detection missions. (abridged)