SIM PlanetQuest key project precursor observations to detect gas giant planets around young stars

We present a review of precursor observing programs for the SIM PlanetQuest Key Project devoted to detecting Jupiter-mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high-contrast images, interferometric data, and radial velocities for stars in both the northern and southern hemispheres. We have completed a high-contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within 1 (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators, and a few stars in Taurus and the Pleiades may have substellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or substellar companions with separations of 5-50 mas. The photometric survey suggests that approximately half of the stars initially selected for this program are variable to a degree ( 1 sigma > 0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets and rank them according to their viability as a result of the observations taken to date. The observable that removes by far the most targets from the SIM young stellar object (YSO) program is photometric variability.