Journal Article

Primordial substructure in the Orion Nebula Cluster

Aylwyn Scally and Cathie Clarke

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 334, issue 1, pages 156-166
Published in print July 2002 | ISSN: 0035-8711
Published online July 2002 | e-ISSN: 1365-2966 | DOI:
Primordial substructure in the Orion Nebula Cluster

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We use numerical N-body simulations of the Orion Nebula Cluster (ONC) to investigate the possibility of substructure in its formation. There is no substructure apparent in the ONC today. However, unless there was a remarkable degree of homogeneity in the molecular cloud from which it formed, it seems unlikely that this would have been true of the cluster in its earliest phase. More plausibly, the early structure of the cluster would have consisted of groups or clumps of subclusters, following the structure of the cloud itself. We have explored the extent to which such subclusters could subsequently have merged, and find that the age of the cluster is a critical factor. The most inhomogeneous initial conditions, comprising a small number of subclusters with many members, are ruled out by an age of 2 Myr or less. There is a considerable amount of freedom in the other direction, however, which suggests that fragmentation in the original cloud is more likely to have been on the scale of small clumps, each producing fewer than 100 stars. These initial subclusters could have been very dense – perhaps two or three orders of magnitude more dense than the core of the ONC today.

Keywords: stellar dynamics; celestial mechanics; open clusters and associations: individual: Orion Nebula Cluster

Journal Article.  6463 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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