The sub-stellar birth rate from UKIDSS
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Author
Day-Jones, A. C.
Marocco, F.
Pinfield, D.J.
Zhang, Z. H.
Burningham, B.
Deacon, Niall
Ruiz, M. T.
Gallardo, J.
Jones, H.R.A.
Lucas, P.W.
Jenkins, J. S.
Gomes, J.
Folkes, S. L.
Clarke, J. R. A.
Attention
2299/13870
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.
Publication date
2013-04Published in
Monthly Notices of the Royal Astronomical SocietyPublished version
https://doi.org/10.1093/mnras/sts685Other links
http://hdl.handle.net/2299/13870Metadata
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