Astrophys. J., 732, 86 (2011/May-2)
Substellar objects in nearby young clusters (SONYC). III. Chamaeleon-I.
MUZIC K., SCHOLZ A., GEERS V., FISSEL L. and JAYAWARDHANA R.
Abstract (from CDS):
SONYC–Substellar Objects in Nearby Young Clusters–is a survey program to investigate the frequency and properties of substellar objects with masses down to a few times that of Jupiter in nearby star-forming regions. In this third paper, we present our recent results in the Chamaeleon-I star-forming region. We have carried out deep optical and near-infrared imaging in four bands (I, z, J, KS) using VIMOS on the European Southern Observatory Very Large Telescope (VLT) and SOFI on the New Technology Telescope, and combined our data with mid-infrared data from the Spitzer Space Telescope. The survey covers ∼0.25 deg2 on the sky and reaches completeness limits of 23.0 in the I band, 18.3 in the J band, and 16.7 in the KSband. Follow-up spectroscopy of the candidates selected from the optical photometry (I ≲ 21) was carried out using the multi-object spectrograph VIMOS on the VLT. We identify 13 objects consistent with M spectral types, 11 of which are previously known M dwarfs with confirmed membership in the cluster. The two newly reported objects have effective temperatures above the substellar limit. We also present two new candidate members of Chamaeleon-I, selected from our JK photometry combined with the Spitzer data. Based on the results of our survey, we estimate that the number of missing very low mass members down to ∼0.008 M☉ and AV ≤ 5 is ≤ 7, i.e., ≤ 3% of the total cluster population according to the current census.
brown dwarfs - stars: low-mass
Table 2: [MSG2011] NN N=13 among (Nos 1-28). Table 3: [MSG2011] IRN (Nos IR1-IR2).
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