ESTIMATES OF THE PLANET YIELD FROM GROUND-BASED HIGH-CONTRAST IMAGING OBSERVATIONS AS A FUNCTION OF STELLAR MASS

Abstract

We use Monte Carlo simulations to estimate the number of extrasolar planets that are directly detectable in the solar-neighborhood using current and forthcoming high-contrast imaging instruments. Our calculations take into account the important factors that govern the likelihood for imaging a planet, including the statistical properties of nearby stars, correlations between star and planet properties, observational effects, and selection criteria. We consider several different ground-based surveys and express the resulting yields as a function of stellar mass. Selecting targets based on their youth, visual brightness, and proximity to the Sun, we find that strong correlations between star mass and planet properties are required to reproduce high-contrast imaging results to date. Using the most recent empirical findings for the occurrence rate of planets from RV surveys, our simulations indicate that extrapolation of the Doppler planet population to separations accessible to high-contrast instruments provides excellent agreement between simulations and observations using present-day contrast levels. In addition to being intrinsically young and bright to serve as their own beacon for AO correction, A-stars have a high planet occurrence rate and propensity to form massive planets in wide orbits, making them ideal targets. The same effects responsible for creating a multitude of detectable planets around massive stars conspire to reduce the number orbiting low-mass stars. However, in the case of a young stellar cluster, MK-stars can dominate the number of detections because of an observational bias related to small number statistics. The degree to which low-mass stars produce the most detections in this special case depends upon formation mechanism. [Abridged]