Probing the upper Scorpius mass function in the planetary-mass regime

We present the results of a deep ZYJ near-infrared survey of 13.5 deg² in the Upper Scorpius (USco) OB association. We photometrically selected ∼100 cluster member candidates with masses in the range of 30–5 Jupiters, according to state-of-the-art evolutionary models. We identified 67 ZYJ candidates as bona fide members, based on complementary photometry and astrometry. We also extracted five candidates detected with Visible and Infrared Survey Telescope for Astronomy at YJ only. One is excluded using deep optical z-band imaging, while two are likely non-members, and three remain as potential members. We conclude that the USco mass function is more likely decreasing in the planetary-mass regime (although a flat mass function cannot yet be discarded), consistent with surveys in other regions.