Substellar Objects in Nearby Young Clusters (SONYC) III: Chamaeleon-I

Abstract

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 ESO Very Large Telescope 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 sqdeg on the sky, and reaches completeness limits of 23.0 in the I-band, 18.3 in the J-band, and 16.7 in Ks-band. 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 2 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 MSun and Av <= 5 is <= 7, i.e. <= 3% of the total cluster population according to the current census.

Accepted by Astrophysical Journal

References in corpus (13)

• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• The Stellar Population of the Chamaeleon I Star-Forming Region
• The Disk Population of the Chamaeleon I Star-Forming Region
• Rotation and accretion of very low mass objects in the SigmaOri cluster
• Discovery of a Young Substellar Companion in Chamaeleon
• The potential for Earth-mass planet formation around brown dwarfs
• Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
• A Multiplicity Census of Young Stars in Chamaeleon I
• New Low-Mass Stars and Brown Dwarfs with Disks in the Chamaeleon I Star-Forming Region
• Substellar Objects in Nearby Young Clusters (SONYC): The bottom of the Initial Mass Function in NGC1333
• Spectroscopy of planetary mass brown dwarfs in Orion
• Substellar Objects in Nearby Young Clusters (SONYC) II: The Brown Dwarf Population of Rho Ophiuchi
• A Methane Imaging Survey for T Dwarf Candidates in Rho Ophiuchi

Cited by in corpus (11)

• Substellar Objects in Nearby Young Clusters (SONYC) IV: A census of very low mass objects in NGC1333
• Substellar Objects in Nearby Young Clusters (SONYC) V: New brown dwarfs in rho Ophiuchi
• Testing the universality of the IMF with Bayesian statistics: young clusters
• Substellar Objects in Nearby Young Clusters (SONYC) IX: The planetary-mass domain of Chamaeleon-I and updated mass function in Lupus-3
• Constraining the Frequency of Free-Floating Planets from a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results
• Substellar Objects in Nearby Young Clusters (SONYC) VIII: Substellar population in Lupus 3
• A survey for planetary-mass brown dwarfs in the Chamaeleon I star-forming region
• A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars
• New low-mass members of Chamaeleon I and $\epsilon$ Cha
• A Significant Population of Candidate New Members of the Rho Ophiuchi Cluster
• Multi-Object and Long-Slit Spectroscopy of Very Low Mass Brown Dwarfs in Orion Nebular Cluster