The search for protoplanets with aperture masking (SPAM) survey: new constraints on the protoplanet population and technical achievements of aperture masking

Material reservoirs within protoplanetary disks are evident progenitors of protoplanets. Interferometric direct imaging techniques, such as non-redundant masking (NRM), allow us to characterize gas giant accretion timescales and dynamical interactions by imaging protoplanetary disks that exhibit evidence of planet formation. By using NRM we can achieve angular resolution down to and within the diffraction limit, and image planet formation on solar system scales. We present the results of a Keck/NIRC2 NRM direct imaging survey with a sample of 17/30 protoplanetary disks. We present upper limits on protoplanet masses times accretion rates and characterize disk structure at spatial separations down to ~7 AU in 17 of the 30 targets. We highlight the detection capabilities and discuss the limitations of Keck/NIRC2 NRM and motivate the need for future spectroscopic NRM facilities, such as Keck/SCALES.