The Hawaii Infrared Parallax Program. IV. A Comprehensive Parallax Survey of L0-T8 dwarfs with UKIRT

TL;DR

This paper provides the largest infrared parallax survey of L0-T8 brown dwarfs, offering precise measurements that enable comprehensive population studies and improve upon previous data, including Gaia comparisons.

Contribution

It presents new parallaxes for 165 objects, improves measurements for 53, and offers the first parallaxes for 165 objects, significantly expanding the volume-limited sample of brown dwarfs.

Findings

First parallaxes for 165 objects.

Improved measurements for 53 objects.

Consistent Gaia DR2 parallaxes for 104 objects.

Abstract

We present parallaxes, proper motions, and $J$-band photometry for 348 L and T dwarfs measured using the wide-field near-infrared camera WFCAM on the United Kingdom Infrared Telescope. This is the largest single batch of infrared parallaxes for brown dwarfs to date. Our parallaxes have a median uncertainty of 3.5 mas, similar to most previous ground-based infrared parallax surveys. Our target list was designed to complete a volume-limited parallax sample of L0-T8 dwarfs out to 25 pc spanning declinations $-30^\circ$ to $+60^\circ$ (68% of the sky). We report the first parallaxes for 165 objects, and we improve on previous measurements for another 53 objects. Our targets include 104 objects (mostly early-L dwarfs) having $Gaia$ DR2 parallax measurements, with which our parallaxes are consistent. We include an extensive comparison of previous literature parallaxes for L and T dwarfs with both our results and $Gaia$ DR2 measurements, identifying systematic offsets for some previous surveys. Our parallaxes confirm that 14 objects previously identified as wide common proper motion companions to main-sequence stars have distances consistent with companionship. We also report new $J_\mathrm{MKO}$ photometry for our targets, including the first measurements for 193 of our targets and improvements over previously published $J_\mathrm{MKO}$ photometry for another 60 targets. Altogether, our parallaxes will enable the first population studies using a volume-limited sample spanning spectral types L0-T8 defined entirely by parallaxes.