A photometric and astrometric investigation of the brown dwarfs in Blanco 1

TL;DR

This study combines photometric and astrometric data to identify low-mass stars and brown dwarfs in Blanco 1, discovering new candidates and confirming the lowest mass member, while analyzing the cluster's mass function.

Contribution

It provides a new catalog of low-mass and substellar members of Blanco 1 using multi-band data and proper motions, including newly discovered objects and the lowest mass candidate.

Findings

Identified 44 candidate members, including 5 new discoveries.

Confirmed the lowest mass candidate at 29 Jupiter masses.

Determined the cluster's mass function slope as +0.93.

Abstract

We present the results of a photometric and astrometric study of the low mass stellar and substellar population of the young open cluster Blanco 1. We have exploited J band data, obtained recently with the Wide Field Camera (WFCAM) on the United Kingdom InfraRed Telescope (UKIRT), and 10 year old I and z band optical imaging from CFH12k and Canada France Hawaii Telescope (CFHT), to identify 44 candidate low mass stellar and substellar members, in an area of 2 sq. degrees, on the basis of their colours and proper motions. This sample includes five sources which are newly discovered. We also confirm the lowest mass candidate member of Blanco 1 unearthed so far (29MJup). We determine the cluster mass function to have a slope of alpha=+0.93, assuming it to have a power law form. This is high, but nearly consistent with previous studies of the cluster (to within the errors), and also that of its much better studied northern hemisphere analogue, the Pleiades.