The Gemini NICI Planet-Finding Campaign: Statistical Constraints on Planet Populations

The Gemini NICI (Near Infrared Coronagraphic Imager) Planet-Finding Campaign is already the largest, deepest direct imaging survey for close-in extrasolar planet ever conducted, given the >200 stars observed to date, with median contrasts of 15 magnitudes at 1". We describe the quantitative methodology used to design the campaign target list and survey design, in order to maximize the likelihood of detecting planets with NICI, and to study the dependence of planet distributions on stellar mass and age. We also present early results from our analysis of the statistical constraints placed on extrasolar planet populations. Using Monte Carlo simulations of planet populations, and the first 120 stars observed by the survey, we are able to place much stronger constraints on the distribution of long-period extrasolar planets than has been found to date, closing the gap between direct imaging and radial velocity studies of the semi-major axis distribution of extrasolar giant planets, providing a key test of planet formation theory. Our analysis shows that fewer than 20% of solar-type stars can have planets more massive than two Jupiter masses in orbits beyond 10 AU. Using a mass and orbital distribution for Jovian planets derived from radial velocity planets, we find an outer semi-major axis for gas-giant planets of 33 AU at 95% confidence.