# A survey for planetary-mass brown dwarfs in the Chamaeleon I star-forming region

## TL;DR

This study searches for planetary-mass brown dwarfs in Chamaeleon I, confirming six new members with some potentially having disks, and highlights the need for deeper observations to determine the initial mass function's lower limit.

## Contribution

It provides the first identification of planetary-mass brown dwarfs in Chamaeleon I using multi-wavelength data and spectroscopy, including the discovery of objects as low as 3 M_Jup.

## Key findings

- Six new late-type members confirmed, including one with the lowest extinction-corrected M_K.
- Detection of potential disks around some of the new brown dwarfs.
- Extension of the mass function below 6-10 M_Jup, indicating the need for deeper surveys.

## Abstract

We have performed a search for planetary-mass brown dwarfs in the Chamaeleon I star-forming region using proper motions and photometry measured from optical and infrared images from the Spitzer Space Telescope, the Hubble Space Telescope, and ground-based facilities. Through near-infrared spectroscopy at Gemini Observatory, we have confirmed six of the candidates as new late-type members of Chamaeleon I >M7.75. One of these objects, Cha J11110675-7636030, has the faintest extinction-corrected M_K among known members, which corresponds to a mass of 3-6 M_Jup according to evolutionary models. That object and two other new members have redder mid-IR colors than young photospheres at <M9.5, which may indicate the presence of disks. However, since those objects may be later than M9.5 and the mid-IR colors of young photospheres are ill-defined at those types, we cannot determine conclusively whether color excesses from disks are present. If Cha J11110675-7636030 does have a disk, it would be a contender for the least-massive known brown dwarf with a disk. Since the new brown dwarfs that we have found extend below our completeness limit of 6-10 M_Jup, deeper observations are needed to measure the minimum mass of the initial mass function in Chamaeleon I.