SCYON Abstract

Received on September 16 2009

Young T-Dwarf Candidates in IC 348

Authors	A.S.M. Burgess, E. Moraux, J. Bouvier, C. Marmo, L. Albert, and H. Bouy
Affiliation	Laboratoire d’Astrophysique, Observatoire de Grenoble Institut d’Astrophysique de Paris Canada-France-Hawaii Telescope Corporation Instituto de Astrofísica de Canarias
Accepted by	Astronomy & Astrophysics
Contact	aburgess@obs.ujf-grenoble.fr
URL	http://arxiv.org/abs/0909.0917
Links	IC 348

Abstract

The determination of the lower-end of the initial mass function (IMF) provides strong constraints on star formation theories. We report here on a search for isolated planetary-mass objects in the 3 Myr-old star-forming region IC 348. Deep, narrowband CH4off and CH4on images were obtained with CFHT/WIRCam over 0.11 sq.deg. in the central part of IC 348 to identify young T-dwarfs from their 1.6 um methane absorption bands. We report three faint T-dwarf candidates with CH4on-CH4off colours > 0.4 mag. Extinction was estimated for each candidate and lies in the range Av ~ 5-12 mag. Comparisons with T-dwarf spectral models, and colour/colour and colour/magnitude diagrams, reject two of the three candidates because of their extreme z' - J blueness. The one remaining object is not thought to be a foreground field dwarf because of a number density argument and also its strong extinction Av - 12 mag, or thought to be a background field T-dwarf which would be expected to be much fainter. Models and diagrams give this object a preliminary T6 spectral type. With a few Jupiter masses, the young T-dwarf candidate reported here is potentially amongst the youngest, lowest mass objects detected in a star-forming region so far. Its frequency is consistent with the extrapolation of current lognormal IMF estimates down to the planetary mass domain.