Low mass T Tauri and young brown dwarf candidates in the Chamaeleon II dark cloud found by DENIS

¹ Observatoire de la Côte d'Azur, Département Fresnel, 06304 Nice Cedex, France e-mail: epchtein@obs-nice.fr
² California Institute of Technology, IPAC/JPL, Pasadena, CA 91109, USA e-mail: laurent@ipac.caltech.edu

Corresponding author: M. H. Vuong, vuong@cea.fr

Received: 11 May 2001
Accepted: 5 September 2001

Abstract

We define a sample designed to select low-mass T Tauri stars and young brown dwarfs using DENIS data in the Chamaeleon II molecular cloud. We use a star count method to construct an extinction map of the Chamaeleon II cloud. We select our low-mass T Tauri star and young brown dwarf candidates by their strong infrared color excess in the color-color dereddened diagram. We retain only objects with colors , and spatially distributed in groups around the cloud cores. This provides a sample of 70 stars of which 4 are previously known T Tauri stars. We have carefully checked the reliability of all these objects by visual inspection of the DENIS images. Thanks to the association of the optical I band to the infra-red J and K_s bands in DENIS, we can apply this selection method to all star formation regions observed in the southern hemisphere. We also identify six DENIS sources with X-ray sources detected by ROSAT. Assuming that they are reliable low-mass candidates and using the evolutionary models for low-mass stars, we estimate the age of these sources between 1 Myr and <10 Myr.