Praesepe (NGC 2632) and its tidal tails

Abstract

Within a 400 pc sphere around the Sun, we search for Praesepe's tidal tails in the Gaia DR2 dataset. We used a modified convergent-point method to search for stars with space velocities close to the space velocity of the Praesepe cluster. We find a clear indication for the existence of Praesepe's tidal tails, both extending up to 165~pc from the centre of the cluster. A total of 1393 stars populate the cluster and its tails, giving a total mass of 794 M_Sun. We determined a tidal radius of 10.77 pc for the cluster and a tidal mass of 483 M_Sun. The corresponding half-mass radius is 4.8 pc. We also found clear indication for mass segregation in the cluster. The tidal tails outside 2 tidal radii are populated by 389 stars. The total contamination of our sample by field stars lies between 50 to 100 stars or 3.6 to 7.2 per cent. We used an astrometrically and photometrically clean sub-sample of Gaia DR2 which makes our Praesepe sample incomplete beyond M_G ~ 12.0 mag, which corresponds to about 0.25 M_Sun. A comparison with an N-body model of the cluster and its tails shows remarkably good coincidence. Three new white dwarfs are found in the tails.

6 pages, 5 figures. Accepted by Astronomy and Astrophysics

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• Diagnosing the Stellar Population and Tidal Structure of the Blanco1 Star Cluster
• Differential abundances of open clusters and their tidal tails: chemical tagging and chemical homogeneity
• Kinematic modelling of clusters with Gaia: the Death Throes of the Hyades
• Tidal tails of open star clusters as probes to early gas expulsion II: Predictions for Gaia
• A binary star sequence in the outskirts of the disrupting Galactic open cluster UBC 274
• The 800pc long tidal tails of the Hyades star cluster: Possible discovery of candidate epicyclic overdensities from an open star cluster