On the nature of rotation in the Praesepe cluster

TL;DR

This study uses Gaia EDR3 data to analyze the internal rotation of the Praesepe cluster, revealing its rotation velocity, axis orientation, and consistency with classical Newtonian dynamics.

Contribution

Developed a new methodology to determine the rotational properties of Praesepe using high-precision astrometric data, providing detailed kinematic insights.

Findings

Praesepe's rotation velocity is approximately 0.2 km/s.

The rotation axis is tilted about 41 degrees relative to the Galactic plane.

Member star rotation follows classical Newtonian theorems.

Abstract

Although a large number of Galactic open clusters (OCs) have been identified, the internal kinematic properties (e.g., rotation) of almost all the known OCs are still far from clear. With the high-precision astrometric data of Gaia EDR3, we have developed a methodology to unveil the rotational properties of the Praesepe cluster. Statistics of the three-dimensional residual motions of the member stars reveal the presence of Praesepe's rotation and determine its spatial rotation axis. The mean rotation velocity of the Praesepe cluster within its tidal radius is estimated to be 0.2 $\pm$ 0.05 km s$^{-1}$, and the corresponding rotation axis is tilted in relation to the Galactic plane with an angle of 41 $\pm$ 12 degree. We also analysed the rms rotational velocity of the member stars around the rotation axis, and found that the rotation of the member stars within the tidal radius of Praesepe probably follows the Newton's classical theorems.