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

TL;DR

This study conducts a deep near-infrared survey of the Upper Scorpius region, identifying potential planetary-mass members and analyzing the mass function, which appears to decline in the planetary-mass regime.

Contribution

It provides new photometric and astrometric data on low-mass objects in Upper Scorpius, refining the understanding of the region's mass function at planetary masses.

Findings

Mass function likely decreases in planetary-mass regime

Identified 67 bona-fide cluster members

Detected additional candidates with YJ-only photometry

Abstract

We present the results of a deep ZYJ near-infrared survey of 13.5 square degrees in the Upper Scorpius (USco) OB association. We photometrically selected ~100 cluster member candidates with masses in the range 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 VISTA 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.