Star cluster kinematics with AAOmega

TL;DR

This paper demonstrates the capabilities of the AAOmega spectrograph for star cluster kinematics, showcasing rapid and precise radial velocity measurements across different cluster types with just three nights of data.

Contribution

It presents new case studies using AAOmega data to determine cluster membership and velocity dispersions, highlighting the instrument's efficiency and potential for resolving longstanding questions.

Findings

Effective membership determination for open clusters NGC 2451A and B

Assessment of planetary nebula NGC 2438's cluster membership

Measurement of velocity dispersions in globular clusters M4 and NGC 6144

Abstract

The high-resolution setup of the AAOmega spectrograph on the Anglo-Australian Telescope makes it a beautiful radial velocity machine, with which one can measure velocities of up to 350-360 stars per exposure to +/-1--2 km/s in a 2-degree field of view. Here we present three case studies of star cluster kinematics, each based on data obtained on three nights in February 2008. The specific aims included: (i) cluster membership determination for NGC 2451A and B, two nearby open clusters in the same line-of-sight; (ii) a study of possible membership of the planetary nebula NGC 2438 in the open cluster M46; and (iii) the radial velocity dispersion of M4 and NGC 6144, a pair of two globular clusters near Antares. The results which came out of only three nights of AAT time illustrate very nicely the potential of the instrument and, for example, how quickly one can resolve decades of contradiction in less than two hours of net observing time.