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The spatial evolution of stellar structures in the LMC/SMC

Published online by Cambridge University Press:  01 July 2008

Nate Bastian ,
Mark Gieles ,
Barbara Ercolano  and
Robert Gutermuth
Nate Bastian
Affiliation:
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK email: bastian@ast.cam.ac.uk; be@ast.cam.ac.uk
Mark Gieles
Affiliation:
European Southern Observatory, Casilla 19001, Santiago 19, Chile email: mgieles@eso.org
Barbara Ercolano
Affiliation:
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK email: bastian@ast.cam.ac.uk; be@ast.cam.ac.uk
Robert Gutermuth
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA email: rgutermuth@cfa.harvard.edu
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Abstract

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We present an analysis of the spatial distribution of various stellar populations within the Large and Small Magellanic Clouds. We use optically selected stellar samples with mean ages between ~9 and ~1000 Myr, and existing stellar cluster catalogues to investigate how stellar structures form and evolve within the LMC/SMC. We use two statistical techniques to study the evolution of structure within these galaxies, the Q-parameter and the two-point correlation function (TPCF). In both galaxies we find the stars are born with a high degree of substructure (i.e. are highly fractal) and that the stellar distribution approaches that of the “background” population on timescales similar to the crossing times of the galaxy (~ 80 Myr & ~ 150 Myr for the SMC/LMC respectively). By comparing our observations to simple models of structural evolution we find that “popping star clusters” do not significantly influence structural evolution in these galaxies. Instead we argue that general galactic dynamics are the main drivers, and that substructure will be erased in approximately the crossing time, regardless of spatial scale, from small clusters to whole galaxies. This can explain why many young Galactic clusters have high degrees of substructure, while others are smooth and centrally concentrated. We conclude with a general discussion on cluster “infant mortality”, in an attempt to clarify the time/spatial scales involved.

Keywords

stars: kinematicsMagellanic Cloudsgalaxies: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S256: The Magellanic System: Stars, Gas, and Galaxies , July 2008 , pp. 45 - 50
Copyright
Copyright © International Astronomical Union 2009

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