The substellar content of the ONC

TL;DR

This paper presents deep infrared observations of the Orion Nebula Cluster, revealing its substellar initial mass function with new peaks in the brown dwarf and planetary mass regimes, aiding understanding of star formation.

Contribution

It provides the first detailed substellar mass function of the ONC extending into planetary masses with unprecedented sensitivity.

Findings

Identification of a second peak at ~0.04 M_sun in the SIMF

Detection of a possible third rise in the free-floating planetary mass regime

Refinement of the substellar IMF shape in the ONC

Abstract

The Substellar Initial Mass Function (SIMF) of many star-forming regions is still poorly known but the detailed knowledge of its shape will help to distinguish among the substellar formation theories. The Orion Nebula Cluster (ONC) is one of the most extensively studied star forming regions. We here present deep, wide-field JHK observations of the ONC taken with HAWK-I@VLT. These observations extend the IMF into the brown dwarf and free-floating planetary mass regime with unprecedented sensitivity. To obtain a clean sample of ONC members, we exclude potential background sources with the help of CO extinction maps. Masses are assigned by means of evolutionary tracks in the H vs. J-H Color-Magnitude Diagram (CMD). Besides the well known stellar peak at ~0.25 M_sun we find a pronounced second peak at ~0.04 M_sun in the SIMF and indications for a third rise in the free-floating planetary mass regime.