Astronomy and Astrophysics, volume 508, 823-831 (2009/12-3)
Young T-dwarf candidates in IC 348.
BURGESS A.S.M., MORAUX E., BOUVIER J., MARMO C., ALBERT L. and BOUY H.
Abstract (from CDS):
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 3Myr-old star-forming region IC 348. Deep, narrowband CH4off and CH4on images were obtained with CFHT/WIRCam over 0.11sq.deg. in the central part of IC 348 to identify young T-dwarfs from their 1.6µm methane absorption bands. We report three faint T-dwarf candidates with CH4on-CH4off colours >0.4mag. Extinction was estimated for each candidate and lies in the range AV∼5-12mag. 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∼12mag, 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.
stars: formation - stars: low-mass, brown dwarfs - open clusters and associations: individual: IC 348 - stars: luminosity function, mass function - infrared: stars
Tables 3-4: [BMB2009] IC348 CH4 N (Nos 1-3).
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