# Multiple Populations of Extrasolar Gas Giants

## TL;DR

This study analyzes 569 gaseous planets and brown dwarfs to explore their formation mechanisms, revealing a hybrid scenario involving core accretion and disk instability, especially around early-type stars and across different mass regimes.

## Contribution

It provides a comprehensive cluster analysis of exoplanet samples, highlighting the coexistence of formation processes and the influence of host star type and metallicity.

## Key findings

- Mass boundary at 4 and 25 Jupiter masses indicates different formation regimes.
- Disk instability is more significant around early-type stars.
- A hybrid formation scenario explains the diversity of observed exoplanets.

## Abstract

There are two planetary formation scenarios: core accretion and gravitational disk instability. Based on the fact that gaseous objects are preferentially observed around metal-rich host stars, most extra-solar gaseous objects discovered to date are thought to have been formed by core accretion. Here, we present 569 samples of gaseous planets and brown dwarfs found in 485 planetary systems that span three mass regimes with boundary values at 4 and 25 Jupiter-mass masses through performing cluster analyses of these samples regarding the host-star metallicity, after minimizing the impact of the selection effect of radial-velocity measurement on the cluster analysis. The larger mass is thought to be the upper mass limit of the objects that were formed during the planetary formation processes. In contrast, the lower mass limit appears to reflect the difference between planetary formation processes around early-type and G-type stars; disk instability plays a greater role in the planetary formation process around early-type stars than that around G-type stars. Population with masses between 4 and 25 Jupiter masses that orbit early-type stars comprise planets formed not only via the core-accretion process but also via gravitational disk instability because the population preferentially orbits metal-poor stars or is independent of the host-star metallicity. Therefore, it is essential to have a hybrid scenario for the planetary formation of the diverse systems.