The SONYC survey: Towards a complete census of brown dwarfs in star forming regions

TL;DR

The SONYC survey aims to comprehensively catalog substellar objects in nearby star-forming regions, revealing the distribution and frequency of brown dwarfs and planetary-mass objects, and their contribution to cluster mass.

Contribution

This study provides the first extensive census of substellar objects down to planetary masses in multiple star-forming regions, including new discoveries and detailed mass function analysis.

Findings

Over 60 new substellar objects identified.

Brown dwarf to star ratio between 2 and 6.

Planetary-mass objects are 20-50 times less common than stars.

Abstract

SONYC, short for "Substellar Objects in Nearby Young Clusters", is a survey program to provide a census of the substellar population in nearby star forming regions. We have conducted deep optical and near-infrared photometry in five young regions (NGC1333, rho Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3), combined with proper motions, and followed by extensive spectroscopic campaigns with Subaru and VLT, in which we have obtained more than 700 spectra of candidate low-mass objects. We have identified and characterized more than 60 new substellar objects, among them a handful of objects with masses close to, or below the Deuterium burning limit. Through SONYC and surveys by other groups, the substellar IMF is now well characterized down to ~ 5 - 10 MJup, and we find that the ratio of the number of stars with respect to brown dwarfs lies between 2 and 6. A comprehensive survey of NGC 1333 reveals that, down to ~5MJup, free-floating objects with planetary masses are 20-50 times less numerous than stars, i.e. their total contribution to the mass budget of the clusters can be neglected.