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Centro de Astrofísica da Universidade do Porto

The structures of embedded clusters in the Perseus, Serpens and Ophiuchus molecular clouds

S. Schmeja, M. S. N. Kumar, B. Ferreira

Abstract
The young stellar population data of the Perseus, Ophiuchus and Serpens molecu-
lar clouds are obtained from the Spitzer c2d legacy survey in order to investigate
the spatial structure of embedded clusters using the nearest neighbour and minimum
spanning tree method. We identify the embedded clusters in these clouds as density
enhancements and analyse the clustering parameter Q with respect to source lumi-
nosity and evolutionary stage. This analysis shows that the older Class 2/3 objects
are more centrally condensed than the younger Class 0/1 protostars, indicating that
clusters evolve from an initial hierarchical configuration to a centrally condensed one.
Only IC 348 and the Serpens core, the older clusters in the sample, shows signs of
mass segregation (indicated by the dependence of Q on the source magnitude), point-
ing to a significant effect of dynamical interactions after a few Myr. The structure of
a cluster may also be linked to the turbulent energy in the natal cloud as the most
centrally condensed cluster is found in the cloud with the lowest Mach number and
vice versa. In general these results agree well with theoretical scenarios of star cluster
formation by gravoturbulent fragmentation.

Keywords
methods: statistical – stars: formation – ISM: clouds – ISM: kinematics and dynamics – open clusters and associations: general – infrared: stars.

Monthly Notices of the Royal Astronomical Society
Volume 389, Page 1209
September 2008

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