The Gemini NICI Planet-Finding Campaign: The Frequency of Planets around Young Moving Group Stars

TL;DR

This study conducted a direct imaging survey of 80 young moving group stars, finding a low frequency of giant planets at wide separations, and discovered four substellar or stellar companions.

Contribution

It provides new constraints on the occurrence rate of giant planets around young stars using high-contrast imaging and Bayesian analysis, with the first direct imaging survey targeting multiple moving groups.

Findings

Detected four co-moving companions of brown dwarf or stellar mass.

Restricted the frequency of 1-20 MJup planets at 10-150 AU to less than 18% (DUSTY) and 6% (COND).

Achieved median contrasts of ΔH=13.9 mag at 1" and 15.1 mag at 2".

Abstract

We report results of a direct imaging survey for giant planets around 80 members of the Beta Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra moving groups, observed as part of the Gemini NICI Planet-Finding Campaign. For this sample, we obtained median contrasts of \Delta H=13.9 mag at 1" in combined CH4 narrowband ADI+SDI mode and median contrasts of \Delta H=15.1 mag at 2" in H-band ADI mode. We found numerous (>70) candidate companions in our survey images. Some of these candidates were rejected as common-proper motion companions using archival data; we reobserved with NICI all other candidates that lay within 400 AU of the star and were not in dense stellar fields. The vast majority of candidate companions were confirmed as background objects from archival observations and/or dedicated NICI campaign followup. Four co-moving companions of brown dwarf or stellar mass were discovered in this moving group sample: PZ Tel B (36+-6 MJup, 16.4+-1.0 AU, Biller et al. 2010), CD -35 2722B (31+-8 MJup, 67+-4 AU, Wahhaj et al. 2011), HD 12894B (0.46+-0.08 MSun, 15.7+-1.0 AU), and BD+07 1919C (0.20+-0.03 MSun, 12.5+-1.4 AU). From a Bayesian analysis of the achieved H band ADI and ASDI contrasts, using power-law models of planet distributions and hot-start evolutionary models, we restrict the frequency of 1--20 MJup companions at semi-major axes from 10--150 AU to <18% at a 95.4% confidence level using DUSTY models and to <6% at a 95.4% using COND models.