A 3D view of the Hyades stellar and sub-stellar population

Abstract

Aims. Our scientific goal is to provide a 3D map of the nearest open cluster to the Sun, the Hyades, combining the recent release of Gaia astrometric data, ground-based parallaxes of sub-stellar member candidates and photometric data from surveys which cover large areas of the cluster. Methods. We combined the second Gaia release with ground-based H-band parallaxes obtained with the infrared camera on the 2 m robotic Liverpool telescope to astrometrically identify stellar and sub-stellar members of the Hyades, the nearest open cluster to the Sun. Results. We find 1764 objects within 70° radius from the cluster centre from the Gaia second data release, whose kinematic properties are consistent with the Hyades. We limit our study to 30 pc from the cluster centre (47.03 ± 0.20 pc) where we identify 710 candidate members, including 85 and 385 in the core and tidal radius, respectively. We determine proper motions and parallaxes of eight candidate brown dwarf members and confirm their membership. Using the 3D positions and a model-based mass-luminosity relation we derive a luminosity and mass function in the 0.04–2.5 M⊙ range. We confirm evidence for mass segregation in the Hyades and find a dearth of brown dwarfs in the core of the cluster. From the white dwarf members we estimate an age of 640−49+67 Myr. Conclusions. We identify a list of members in the Hyades cluster from the most massive stars down to the brown dwarfs. We produce for the first time a 3D map of the Hyades cluster in the stellar and sub-stellar regimes and make available the list of candidate members.