First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis

TL;DR

This study reports the first detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis, expanding the known cluster boundary and suggesting a dynamical origin for its current structure.

Contribution

It identifies new low-mass cluster members beyond previous search areas, indicating a stellar halo and challenging prior assumptions about the cluster's initial mass function.

Findings

Discovery of several lithium-rich low-mass stars near Eta Chamaeleontis

Identification of 4 probable and 3 possible new cluster members

Evidence supporting a dynamical origin for the cluster's current configuration

Abstract

We have identified several lithium-rich low-mass (0.08<M<0.3 Msun) stars within 5.5 deg of the young open cluster Eta Chamaeleontis, nearly four times the radius of previous search efforts. Of these stars we propose 4 new probable cluster members, and 3 possible members requiring further investigation. These findings are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an abnormal Initial Mass Function deficient in low-mass objects. Candidates were selected on the basis of DENIS and 2MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy.