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Deep Near-infrared Imaging of the ρ Oph cloud core: Clues to the Origin of the Lowest-mass Brown Dwarfs

Marsh, Kenneth A. and Plavchan, Peter and Kirkpatrick, J. Davy and Lowrance, Patrick J. and Cutri, Roc M. and Velusamy, Thangasamy (2010) Deep Near-infrared Imaging of the ρ Oph cloud core: Clues to the Origin of the Lowest-mass Brown Dwarfs. Astrophysical Journal, 719 (1). pp. 550-560. ISSN 0004-637X.

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A search for young substellar objects in the ρ Oph cloud core region has been made with the aid of multiband profile-fitting point-source photometry of the deep-integration Combined Calibration Scan images of the 2MASS extended mission in the J, H, and K_s bands, and Spitzer IRAC images at 3.6, 4.5, 5.8, and 8.0 μm. The field of view of the combined observations was 1° × 9'.3, and the 5σ limiting magnitude at J was 20.5. Comparison of the observed spectral energy distributions 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, T_(eff). The cluster members are then readily distinguishable from background stars by their locations on a plot of flux density versus T_(eff). The range of estimated T eff values extends down to ~750 K which, based on the COND model, would suggest the presence of objects of sub-Jupiter mass. The results also suggest that the mass function for the ρ Oph cloud resembles that of the σ Orionis cluster based on a recent study, with both rising steadily toward 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 – K_s 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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Marsh, Kenneth A.0000-0003-0107-7803
Plavchan, Peter0000-0002-8864-1667
Kirkpatrick, J. Davy0000-0003-4269-260X
Lowrance, Patrick J.0000-0001-8014-0270
Cutri, Roc M.0000-0002-0077-2305
Additional Information:© 2010 American Astronomical Society. Received 2008 September 19; accepted 2010 June 12; published 2010 July 21. We thank the referee for helpful comments and suggestions. We also thank Tim Thompson for making the IRAC mosaic images, and John Stauffer and Luisa Rebull for helpful discussions. The research utilized data products from 2MASS, a joint project of the University of Massachussetts and IPAC/Caltech, and also archival data from Spitzer, operated by JPL/Caltech under contract to NASA. Use was also made of the SIMBAD database, operated at CDS, Strasbourg, France. The work was carried out at IPAC/Caltech and was supported by a grant from the NASA Astrophysics Data Analysis Program.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:brown dwarfs; infrared: stars; stars: low-mass; stars: pre-main sequence
Issue or Number:1
Classification Code:PACS: 98.38.Dq; 97.20.Vs; 97.10.Me; 97.21.+a; 95.85.Jq
Record Number:CaltechAUTHORS:20100824-131959931
Persistent URL:
Official Citation:Kenneth A. Marsh et al 2010 ApJ 719 550 doi: 10.1088/0004-637X/719/1/550
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19641
Deposited By: Jason Perez
Deposited On:25 Aug 2010 20:48
Last Modified:09 Mar 2020 13:19

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