Extended stellar systems in the solar neighborhood. V. Discovery of coronae of nearby star clusters

Stefan Meingast, João Alves, Alena Rottensteiner

We present a novel view on the morphology and dynamical state of ten

prominent, nearby (≤500 pc), and young (∼30-300 Myr) open star

clusters with Gaia DR2: α Per, Blanco 1, IC 2602, IC 2391, Messier

39, NGC 2451A, NGC 2516, NGC 2547, Platais 9, and the Pleiades. We

introduce a pioneering member-identification method that is informed by

cluster bulk velocities and deconvolves the spatial distribution with a

mixture of Gaussians. Our approach enables inferring the true spatial

distribution of the clusters by effectively filtering field star

contaminants while at the same time mitigating the effect of positional

errors along the line of sight. This first application of the method

reveals vast stellar coronae that extend for ≳100 pc and surround

the cluster cores, which are comparatively tiny and compact. The coronae

and cores form intertwined, coeval, and comoving extended cluster

populations, each encompassing tens of thousands of cubic parsec and

stretching across tens of degrees on the sky. Our analysis shows that

the coronae are gravitationally unbound but largely comprise the bulk of

the stellar mass of the populations. Most systems are in a highly

dynamic state, showing evidence of expansion and sometimes simultaneous

contraction along different spatial axes. The velocity field of the

extended populations for the cluster cores appears asymmetric but is

aligned along a spatial axis unique to each cluster. The overall spatial

distribution and the kinematic signature of the populations are largely

consistent with the differential rotation pattern of the Milky Way. This

finding underlines the important role of global Galactic dynamics in the

fate of stellar systems. Our results highlight the complexity of the

Milky Way's open cluster population and call for a new perspective on

the characterization and dynamical state of open clusters.


The cluster membership table is only available at the CDS via anonymous

ftp to cdsarc.u-strasbg.fr

( or via cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A84


An interactive 3D version of Fig. 8 is available at www.aanda.org

Department of Astrophysics, Research Network Data Science, Dean's office of the Faculty of Earth Sciences, Geography and Astronomy
Astronomy & Astrophysics
Publication date
Peer reviewed
Austrian Fields of Science 2012
103004 Astrophysics
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