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Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5

Cruz, Kelle L. and Kirkpatrick, J. Davy and Burgasser, Adam J. (2009) Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5. Astronomical Journal, 137 (2). pp. 3345-3357. ISSN 0004-6256. doi:10.1088/0004-6256/137/2/3345.

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We present an analysis of 23 L dwarfs whose optical spectra display unusual features. Twenty-one were uncovered during our search for nearby, late-type objects using the Two Micron All Sky Survey, while two were identified in the literature. The unusual spectral features, notably weak FeH molecular absorption and weak Na I and K I doublets, are attributable to low gravity and indicate that these L dwarfs are young, low-mass brown dwarfs. We use these data to expand the spectral classification scheme for L0- to L5-type dwarfs to include three gravity classes. Most of the low-gravity L dwarfs have southerly declinations and distance estimates within 60 pc. Their implied youth, on-sky distribution, and distances suggest that they are members of nearby, intermediate-age (~10-100 Myr), loose associations such as the β Pictoris moving group, the Tucana/Horologium Association, and the AB Doradus moving group. At an age of 30 Myr and with effective temperatures from 1500 to 2400 K, evolutionary models predict masses of 11-30 MJupiter for these objects. One object, 2M 0355+11, with J – Ks = 2.52 ± 0.03, is the reddest L dwarf found in the field and its late spectral type and spectral features indicative of a very low gravity suggest it might also be the lowest mass field L dwarf. However, before ages and masses can be confidently adopted for any of these low-gravity L dwarfs, additional kinematic observations are needed to confirm cluster membership.

Item Type:Article
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URLURL TypeDescription
Cruz, Kelle L.0000-0002-1821-0650
Kirkpatrick, J. Davy0000-0003-4269-260X
Burgasser, Adam J.0000-0002-6523-9536
Additional Information:© 2009. The American Astronomical Society. Received 2008 September 3; accepted 2008 November 28; published 2009 January 28. Print publication: Issue 2 (2009 February). We are grateful for useful discussions with Michael Cushing, Greg Herczeg, Lynne Hillenbrand, Adam Kraus, Dagny Looper, Jessica Lu, Lauren MacArthur, Mark Marley, and I. Neill Reid. We also thank the referee for helpful comments. K.L.C. is supported by NASA through the Spitzer Space Telescope Fellowship Program, through a contract issued by the Jet Propulsion Laboratory, California Institute of Technology under a contract with National Aeronautics and Space Administration. This research was partially supported by a grant from the NASA/NSF NStars initiative, administered by the Jet Propulsion Laboratory, Pasadena, CA. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This publication makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory/California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:open clusters and associations: general; stars: fundamental parameters; stars: late-type; stars: low-mass, brown dwarfs
Issue or Number:2
Record Number:CaltechAUTHORS:CRUaj09
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13217
Deposited By: Archive Administrator
Deposited On:31 Jan 2009 01:45
Last Modified:08 Nov 2021 22:36

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