The sub-stellar birth rate from UKIDSS

A. C. Day-Jones, F. Marocco, D.J. Pinfield, Z. H. Zhang, B. Burningham, Niall Deacon, M. T. Ruiz, J. Gallardo, H.R.A. Jones, P.W. Lucas, J. S. Jenkins, J. Gomes, S. L. Folkes, J. R. A. Clarke

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)
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Abstract

We present a new sample of mid-L to mid-T dwarfs with effective temperatures of 11001700 K selected from the UKIDSS Large Area Survey (LAS) and confirmed with infrared spectra from X-shooter/Very Large Telescope. This effective temperature range is especially sensitive to the formation history of Galactic brown dwarfs and allows us to constrain the form of the sub-stellar birth rate, with sensitivity to differentiate between a flat (stellar like) birth rate and an exponentially declining form. We present the discovery of 63 new L and T dwarfs from the UKIDSS LAS DR7, including the identification of 12 likely unresolved binaries, which form the first complete sub-set from our programme, covering 495 square degrees of sky, complete to J = 18.1. We compare our results for this sub-sample with simulations of differing birth rates for objects of masses 0.10-0.03 M-circle dot and ages 1-10 Gyr. We find that the more extreme birth rates (e. g. a halo type form) can likely be excluded as the true form of the birth rate. In addition, we find that although there is substantial scatter we find a preference for a mass function, with a power-law index a in the range -1 <alpha <0 that is consistent (within the errors) with the studies of late T dwarfs.

Original languageEnglish
Pages (from-to)1171-1187
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume430
Issue number2
DOIs
Publication statusPublished - Apr 2013

Keywords

  • brown dwarfs
  • stars: low-mass
  • stars: luminosity function, mass function
  • ALL-SKY SURVEY
  • DWARF/T-DWARF TRANSITION
  • SUBSTELLAR MASS FUNCTION
  • PROPER MOTION SURVEY
  • SURVEY-EXPLORER WISE
  • STAR-FORMING REGION
  • YOUNG MOVING GROUPS
  • LARGE-AREA SURVEY
  • BROWN DWARFS
  • T-DWARFS

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