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

We have identified several lithium-rich low-mass (0.08 < M < 0.3 M_solar) stars within 5.5° of the young open cluster η Chamaeleontis, nearly four times the radius of previous search efforts. Of these stars, we propose four new probable cluster members and three 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 Two-Micron All-Sky Survey photometry, Naval Observatory Merged Astrometric Catalogue astrometry and extensive follow-up spectroscopy.