The Giant Planet Mass Function Across Stellar Mass and Metallicity: Massive Stars Make Massive Planets

Abstract

Although giant planet occurrence correlates with stellar mass and metallicity, it remains unclear whether these properties also shape the companion mass distribution. We investigate this question using 719 FGKM stars from the California Legacy Survey and companion true-mass constraints from radial velocities and Hipparcos-Gaia astrometry. Our hierarchical occurrence analysis accounts for survey completeness and companion parameter uncertainties over giant planet and brown dwarf masses of M_c=0.4-50 M_Jup and semi-major axes of a=0.1-10 AU. We find that, compared to the rate among our full sample of 0.19 +/- 0.02 planets per star in this interval, giant planet occurrence is significantly enhanced around stars with high mass (M_star>1 M_sun; 0.39 (+0.06/-0.05) planets per star) and high metallicity ([Fe/H]>0.0; 0.30 (+0.04/-0.03) planets per star). We find evidence at the 2-3 sigma level that the planet mass function shape varies with stellar mass, with higher characteristic planet masses around stars with M_star>1 M_sun than around lower-mass hosts, based on differences in both the CDFs of fitted models and constraints on model shape parameters. For the full sample, occurrence declines above a few Jupiter masses and is consistent with either a plateau below ~3 M_Jup or a peak near 1-2 M_Jup. The brown dwarf desert begins at a companion-to-host mass ratio of 0.013-0.02. These results suggest that stellar properties influence not only the frequency of giant companions but also their characteristic masses. Within the core accretion framework, this shift could reflect larger gas reservoirs around more massive stars or earlier core formation in metal-rich disks, allowing greater gas accretion before disk dispersal.