2012MNRAS.424.2778P

In an attempt to study whether the formation of brown dwarfs (BDs) takes place as a scaled-down version of low-mass stars, we conducted Institut de Radioastronomie Millimetrique (IRAM)30m/MAMBO-II observations at 1.2mm in a sample of 12 proto-BD candidates selected from Spitzer/IRAC data in the B213-L1495 clouds in Taurus. Subsequent observations with the Caltech Submillimetre Observatory at 350µm, Very Large Array at 3.6 and 6cm, and IRAM30m/EMIR in the ¹²CO(1–0), ¹³CO(1–0) and N₂H⁺(1–0) transitions were carried out towards the two most promising Spitzer/IRAC source(s), J042118 and J041757. J042118 is associated with a compact (<10arcsec or <1400 au) and faint source at 350µm, while J041757 is associated with a partially resolved ( ∼ 16arcsec or ∼ 2000 au) and stronger source emitting at centimetre wavelengths with a flat spectral index. The corresponding masses of the dust condensations are ∼ 1 and 5M_Jup for J042118 and J041757, respectively. In addition, about 40arcsec to the north-east of J041757, we detect a strong and extended submillimetre source, J041757-NE, which is not associated with near-infrared/far-infrared emission down to our detection limits, but is clearly detected in ¹³CO and N₂H⁺ at ∼ 7km/s, and for which we estimated a total mass of ∼ 100M_Jup, close to the mass required to be gravitationally bound. In summary, our observational strategy has allowed us to find in B213-L1495 two proto-BD candidates and one pre-substellar core candidate, whose properties seem to be consistent with a scaled-down version of low-mass stars.