Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

Open Cluster Groups and Complexes

Dr. Claudia Conrad , Mannheim

It is generally agreed upon that stars form in open clusters and stellar associations, but little is known about structures in the Galactic open cluster population. Are open clusters and stellar associations born isolated or do they prefer to form in groups? Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures. In the past decade studies of open cluster groupings were either based solely on spatial criteria or also included tangential velocities for the identification. In contrast to previous approaches, we assumed that real open cluster groupings occupy a well defined area in the sky and show similar velocity vectors. Therefore, we used 6D phase-space information for the detection of open cluster groupings. In addition, we checked the age spread for the potential candidates, to distinguish between genuine groupings and chance alignments. We explored the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005a,b) and determined 6D phase-space information for 432 out of the 650 listed open clusters and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10-20 km/s. For the verification of the identified structures, we applied Monte-Carlo simulations with randomised samples. For the linking lengths 100 pc and 10 km/s we detected 19 groupings, including 14 pairs, fours groups with 3-5 members, and one complex with 15 members. The Monte-Carlo simulations revealed that in particular the complex is most likely genuine, whereas the pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between the spatial distributions of the young and old cluster population suggested that OC groupings likely originated from a common molecular cloud.

SFB Seminar - The Milky Way System
9 Nov 2016, 16:00
ARI basement seminar room

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