Deep Near-Infrared Imaging of the rho Oph Cloud Core: Clues to the Origin of the Lowest-Mass Brown Dwarfs

Abstract

A search for young substellar objects in the rho Oph cloud core region has been made using the deep-integration Combined Calibration Scan images of the 2MASS extended mission in J, H and Ks bands, and Spitzer IRAC images at 3.6, 4.5, 5.8 and 8.0 microns. The field of view of the combined observations was 1 deg x 9.3 arcmin, and the 5 sigma limiting magnitude at J was 20.5. Comparison of the observed SEDs with the predictions of the COND and DUSTY models, for an assumed age of 1 Myr, supports the identification of many of the sources with brown dwarfs, and enables the estimation of effective temperature, Teff. The cluster members are then readily distinguishable from background stars by their locations on a plot of flux density versus Teff. The range of estimated Teff extends down to ~ 750 K, suggesting the presence of objects of sub-Jupiter mass. The results also suggest that the mass function for the rho Oph cloud resembles that of the sigma Orionis cluster based on a recent study, with both rising towards lower masses. The other main result from our study is the apparent presence of a progressive blueward skew in the distribution of J-H and H-Ks colors, such that the blue end of the range becomes increasingly bluer with increasing magnitude. We suggest that this behavior might be understood in terms of the 'ejected stellar embryo' hypothesis, whereby some of the lowest-mass brown dwarfs could escape to locations close to the front edge of the cloud, and thereby be seen with less extinction.

37 pages, 10 figures; to be published in ApJ

References in corpus (13)

• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• Spitzer/IRAC Photometry of M, L, and T Dwarfs
• The minimum mass for star formation, and the origin of binary brown dwarfs
• A Cross-Match of 2MASS and SDSS: Newly-Found L and T Dwarfs and an Estimate of the Space Densitfy of T Dwarfs
• On the Distance to the Ophiuchus Star-Forming Region
• Young, Low-Mass Brown Dwarfs with Mid-Infrared Excesses
• The Spatial Distribution of Brown Dwarfs in Taurus
• Near-Infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit Candidates
• The low-mass population of the Rho Ophiuchi molecular cloud
• Oph 1622-2405: Not a Planetary-Mass Binary
• The Peculiar Periodic YSO WL 4 in Rho Ophiuchus
• Accretion in rho-Ophiuchi brown dwarfs: infrared hydrogen line ratios
• Spectroscopy of Putative Brown Dwarfs in Taurus

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