A kinematic study of Open Clusters: implications for their origin

TL;DR

This study analyzes the kinematic properties of 481 open clusters to infer their origins, identifying some as likely extragalactic in origin based on orbit and metallicity correlations.

Contribution

It provides a systematic kinematic analysis of open clusters, suggesting some have extragalactic origins due to high velocity impacts and orbit characteristics.

Findings

Identification of four open clusters with extragalactic origin.

Correlation between orbit parameters and metallicity.

Evidence supporting some clusters' origins from Galactic globular clusters.

Abstract

The Galactic population of open clusters provides an insight into star formation in the Galaxy. The open cluster catalogue by Dias et al.(2002b) is a rich source of data, including kinematic information. This large sample made it possible to carry out a systematic analysis of 481 open cluster orbits, using parameters based on orbit eccentricity and separation from the Galactic plane. These two parameters may be indicative of origin, and we find them to be correlated. We also find them to be correlated with metallicity, another parameter suggested elsewhere to be a marker for origin in that high values of any of these two parameters generally indicates a low metallicity ([Fe/H] Solar$<-$0.2 dex). The resulting analysis points to four open clusters in the catalogue being of extra-Galactic origin by impact of high velocity cloud on the disk: Berkeley21, 32, 99, and Melotte66, with a possible further four due to this origin (NGC2158, 2420, 7789, IC1311). A further three may be due to Galactic globular cluster impact on the disk i.e of internal Galactic origin (NGC6791, 1817, and 7044).