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Intermediate to low-mass stellar content of Westerlund 1

Brandner, W.; Clark, J.S.; Stolte, A.; Waters, R.; Negueruela, I. and Goodwin, S.P. (2008). Intermediate to low-mass stellar content of Westerlund 1. Astronomy and Astrophysics, 478(1) pp. 137–149.

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We have analysed near-infrared NTT/SofI observations of the starburst cluster Westerlund 1, which is among the most massive young clusters in the Milky Way. A comparison of colour-magnitude diagrams with theoretical main-sequence and pre-main sequence evolutionary tracks yields improved extinction and distance estimates of AKs = 1.130.03 mag and d = 3.550.17 kpc (DM = 12.750.10 mag). The pre-main sequence population is best fit by a Palla & Stahler isochrone for an age of 3.2 Myr, while the main sequence population is in agreement with a cluster age of 3 to 5 Myr. An analysis of the structural parameters of the cluster yields that the half-mass radius of the cluster population increases towards lower mass, indicative of the presence of mass segregation. The cluster is clearly elongated with an eccentricity of 0.20 for stars with masses between 10 and 32M, and 0.15 for stars with masses in the range 3 to 10M. We derive the slope of the stellar mass function for stars with masses between 3.4 and 27M. In an annulus with radii between 0.75 and 1.5 pc from the cluster centre, we obtain a slope of

Item Type: Journal Article
ISSN: 1432-0746
Keywords: stars: evolution; stars: formation; stars: luminosity function, mass function; stars: pre-main sequence; stars: supernovae: general; Galaxy: open clusters and associations: individual: Westerlund 1
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 12065
Depositing User: Astrid Peterkin
Date Deposited: 20 Oct 2008 08:47
Last Modified: 10 Feb 2012 10:41
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