干旱区生态环境知识资源中心

We describe an ongoing survey to directly detect substellar and planetary companions to nearby young stars. This survey uses adaptive optics and nonredundant aperture-masking interferometry to achieve typical contrast limits of Delta K similar to 6 at the diffraction limit, probing a completely new regime of parameter space. These observations have revealed many new stellar companions, but only a few companions that might be brown dwarfs; this paucity resembles the so-called "brown dwarf desert" that has been observed by RV planet searches. The survey has not detected any extra-solar planets. despite mass detection limits as low as 7 M-Jup, yielding constraints on the population of extrasolar giant planets. Finally, we discuss some of the implications for protoplanetary disk evolution, including potential sources for gap formation and disk dissipation.