47 new T dwarfs from the UKIDSS Large Area Survey

2010/04/13 by Ben Burningham, D. J. Pinfield, P. W. Lucas +22 · 1 citation
Physics and Astronomy · #Absorption (acoustics) #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Field (mathematics) #Monte Carlo method #Physics #Sky #Spectral index #Spectral line #Stars #Statistics #Stellar classification #Stellar, planetary, and galactic studies #Type (biology) #astro-ph.GA #astro-ph.SR

paper · pdf · doi:10.1111/j.1365-2966.2010.16800.x

23 pages, 10 figures. MNRAS accepted. Version 2 includes omitted authors.

arxiv created 2010/04/13 · openalex publication_date 2010/05/01 · arxiv updated 2015/05/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We report the discovery of 47 new T dwarfs in the Fourth Data Release (DR4) from the Large Area Survey (LAS) of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey with spectral types ranging from T0 to T8.5. These bring the total sample of LAS T dwarfs to 80 as of DR4. In assigning spectral types to our objects we have identified eight new spectrally peculiar objects, and divide seven of them into two classes. H<inf>2</inf>O-<it>H</it>-early have a H<inf>2</inf>O-<it>H</it> index that differs with the H<inf>2</inf>O-<it>J</it> index by at least two subtypes. CH<inf>4</inf>-<it>J</it>-early have a CH<inf>4</inf>-<it>J</it> index that disagrees with the H<inf>2</inf>0-<it>J</it> index by at least two subtypes. We have ruled out binarity as a sole explanation for both types of peculiarity, and suggest that they may represent hitherto unrecognized tracers of composition and/or gravity. Clear trends in <it>z</it>′(<it>AB</it>) −<it>J</it> and <it>Y</it>−<it>J</it> are apparent for our sample, consistent with weakening absorption in the red wing of the K <scp>i</scp> line at 0.77 μm with decreasing effective temperature. We have used our sample to estimate space densities for T6–T9 dwarfs. By comparing our sample to Monte Carlo simulations of field T dwarfs for various mass functions of the form ψ(<it>M</it>) ∝ <it>M</it>−α pc−3 M−1<inf>⊙</inf>, we have placed weak constraints on the form of the field mass function. Our analysis suggests that the substellar mass function is declining at lower masses, with negative values of α preferred. This is at odds with results for young clusters that have been generally found to have α > 0.

Citations

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Cited by

• A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density