New brown dwarfs in the south part of the Upper Scorpius Association

TL;DR

This study identifies 19 new brown dwarfs in the southern Upper Scorpius region using infrared survey data and proper motion analysis, contributing to understanding brown dwarf populations in young stellar associations.

Contribution

First identification of brown dwarfs in the southern Upper Scorpius using combined infrared and proper motion data, revealing environmental effects on brown dwarf formation.

Findings

19 new brown dwarfs identified

Brown dwarf to star ratio consistent with other Upper Scorpius regions

Brown dwarf formation rate may depend on environment

Abstract

This paper presents the results of a search for brown dwarfs in the Upper Scorpius Association using data from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey. Candidate young brown dwarfs were first chosen by their position in colour magnitude diagrams with further selection based on proper motions to ensure Upper Scorpius membership. Proper motions were derived by comparing UKIDSS and 2MASS data. Using that method we identify 19 new brown dwarfs in the southern part of the association. In addition there are up to 8 likely members with slightly higher dispersion velocity. The ratio of brown dwarfs to stars was found to be consistent with other areas in Upper Scorpius. It was also found to be similar to other results from young clusters with OB associations, and lower than those without, suggesting the brown dwarf formation rate may be a function of environment.