Measurement of Dependence of Microlensing Planet Frequency on The Host Star Mass and Galactocentric Distance by using a Galactic Model

We measure the dependence of planet frequency on host star mass, ML, and distance from the Galactic center, RL, using a sample of planets discovered by gravitational microlensing. We compare the two-dimensional distribution of the lens-source proper motion, μᵣₑₗ, and the Einstein radius crossing time, tE, measured for 22 planetary events from {suz16} with the distribution expected from Galactic model. Assuming that the planet-hosting probability of a star is proportional to MLᵐ RLʳ, we calculate the likelihood distribution of $(m,r)$. We estimate that r = 0.10+0.51-0.37 and m = 0.50+0.90-0.70 under the assumption that the planet-hosting probability is independent of the mass ratio. %This result suggests that planets are uniformly distributed in the Galaxy and more massive stars are more likely to possess planets. We also divide the planet sample into subsamples based on their mass ratio, q, and estimate that m=-0.08+0.95-0.65 for q < 10⁻³ and 1.25+1.07-1.14 for q > 10⁻³. Although uncertainties are still large, this result implies a possibility that in orbits beyond the snowline, massive planets are more likely to exist around more massive stars whereas low-mass planets exist regardless of their host star mass.