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Cold brown dwarfs with WISE: Y dwarfs and the field mass function

Kirkpatrick, J. D. (2013) Cold brown dwarfs with WISE: Y dwarfs and the field mass function. Astronomische Nachrichten, 334 (1-2). pp. 26-31. ISSN 0004-6337. doi:10.1002/asna.201211759.

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The discovery of a new spectral class – the Y dwarfs – by NASA's Wide-field Infrared Survey Explorer has enabled researchers to study the physics of the coldest brown dwarfs and to determine the prevalence of brown dwarfs in the Milky Way. The boundary between T dwarfs and Y dwarfs roughly coincides with the location where the J – H colors of brown dwarfs, as predicted by models, turn back to the red at effective temperatures below ∼400 K. Preliminary trigonometric parallax measurements show that the T/Y boundary appears also to correspond to the point at which the absolute H (1.6 µm) and W2 (4.6 µm) magnitudes plummet. Using these new distance measurements, it is found that hydrogenburning stars outnumber brown dwarfs by approximately a factor of six in the solar neighborhood. Using simulations describing the mass function as a power law or as a lognormal, we find that both the shape and predicted space densities in the mid-T to early-Y regime can be fit only if these functions are normalized downward to better reflect the relative paucity of brown dwarfs. The sample of currently identified Y dwarfs probes the field mass function to masses of ∼5 M_(Jup), but confirmation of additional, colder Y dwarfs from WISE is needed to determine whether the low-mass limit to star formation has yet been measured.

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Kirkpatrick, J. D.0000-0003-4269-260X
Additional Information:© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Received 2012 Aug 15, accepted 2012 Dec 5; Published online 2013 Feb 1. The author wishes to thank the members of the WISE brown dwarf team for their hard work and dedication, which enabled this paper to be written just two and half years after WISE captured its first photons: Chris Gelino, Mike Cushing, Mike Skrutskie, Ken Marsh, Roger Griffith, Greg Mace, Ned Wright, Peter Eisenhardt, AmyMainzer, Ian McLean, Chas Beichman, Tahina Ramiaramanantsoa, Maggie Thompson, Katholeen Mix, Stephanie Gomillion, Tommy Gautier, and Brian Apodaca. He would also like to thank the team’s collaborators without whom follow-up observations would have taken several additional years: Chris Tinney, Jackie Faherty, Adam Burgasser, Scott Sheppard, Ricky Smart, Guillem Anglada-Escudé, Fred Vrba, Hugh Harris, Josh Bloom, Rob Simcoe, Steve Schurr, Phil Hinz, T. J. Rodigas, Vanessa Bailey, Russell Knox, and Nathan Stock.
Subject Keywords:Galaxy: fundamental parameters – infrared: stars – solar neighborhood – stars: low-mass, brown dwarfs – stars: luminosity function, mass function
Issue or Number:1-2
Record Number:CaltechAUTHORS:20131115-085354248
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Official Citation:Kirkpatrick, J.D. (2013), Cold brown dwarfs with WISE: Y dwarfs and the field mass function. Astron. Nachr., 334: 26–31. doi: 10.1002/asna.201211759
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42484
Deposited By: Bianca Rios
Deposited On:15 Nov 2013 19:11
Last Modified:10 Nov 2021 16:23

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