The low-mass population of the ρ Ophiuchi molecular cloud

Abstract

Context. Star formation theories are currently divergent regarding the fundamental physical processes that dominate the substellar regime. Observations of nearby young open clusters allow the brown dwarf (BD) population to be characterised down to the planetary mass regime, which ultimately must be accommodated by a successful theory. Aims. We hope to uncover the low-mass population of the ρ Ophiuchi molecular cloud and investigate the properties of the newly found brown dwarfs. Methods. We used near-IR deep images (reaching completeness limits of approximately 20.5 mag in J and 18.9 mag in H and K s) taken with the Wide Field IR Camera (WIRCam) at the Canada France Hawaii Telescope (CFHT) to identify candidate members of ρ Oph in the substellar regime. A spectroscopic follow-up of a small sample of the candidates allows us to assess their spectral type and subsequently their temperature and membership. Results. We select 110 candidate members of the ρ Ophiuchi molecular cloud, from which 80 have not previously been associated with the cloud. We observed a small sample of these and spectroscopically confirm six new brown dwarfs with spectral types ranging from M6.5 to M8.25. © 2010 ESO.