Extended stellar systems in the solar neighborhood. I. The tidal tails of the Hyades

Stefan Meingast, João Alves

We report the discovery of two well-defined tidal tails emerging from

the Hyades star cluster. The tails were detected in Gaia DR2 data by

selecting cluster members in the 3D galactocentric cylindrical velocity

space. The robustness of our member selection is reinforced by the fact

that the sources depict an almost noiseless, coeval stellar main

sequence in the observational Hertzsprung-Russel diagram. The spatial

arrangement of the selected members represents a highly flattened shape

with respect to the direction of movement along the clusters' orbit in

the Galaxy. The size of the entire structure, within the limits of the

observations, measures about 200 pc in its largest extent, while being

only about 25 pc thick. This translates into an on-sky extent of well

beyond 100 deg. Intriguingly, a top-down view on the spatial

distribution reveals a distinct S-shape, reminiscent of tidal tails that

have been observed for globular clusters and also of tails that were

modeled for star clusters bound to the Galactic disk. Even more

remarkable, the spatial arrangement as well as the velocity dispersion

of our source selection is in excellent agreement with previously

published theoretical predictions for the tidal tails of the Hyades. An

investigation into observed signatures of equipartition of kinetic

energy, that is, mass segregation, remains unsuccessful, most likely

because of the sensitivity limit for radial velocity measurements with



We acknowledge the simultaneous publication by Röser et al. (2019),

who also used Gaia DR2 to present evidence for the existence of the

Hyades's tidal tails. The authors of both publications did not know

about each other's work and arrived at their conclusions

independently.The catalog is only available at the CDS via anonymous ftp

to cdsarc.u-strasbg.fr

( or via cdsarc.u-strasbg.fr/viz-bin/qcat

Department of Astrophysics, Research Platform Data Science @ Uni Vienna
External organisation(s)
Harvard University
Astronomy & Astrophysics
Publication date
Peer reviewed
Austrian Fields of Science 2012
Astronomy, Astrophysics
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