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          Document History for Document ID 421369

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Document Version Version Comment Date Status
421369.0 [No comment] 28.05.2018 16:41 Released

ID: 421369.0, MPI für Astronomie / Publikationen_mpia
Intermediate to low-mass stellar content of Westerlund 1
Authors:Brandner, W.; Clark, J. S.; Stolte, A.; Waters, R.; Negueruela, I.; Goodwin, S. P.
Language:English
Date of Publication (YYYY-MM-DD):2008
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:A&A
Volume:478
Start Page:137
End Page:149
Review Status:Peer-review
Audience:Experts Only
Abstract / Description: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 = 1.13 ± 0.03 mag and d = 3.55 ± 0.17 kpc (DM = 12.75 ± 0.10 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 32 M_o, and 0.15 for stars with masses in the range 3 to 10 M_o. We derive the slope of the stellar mass function for stars with masses between 3.4 and 27 M_o. In an annulus with radii between 0.75 and 1.5 pc from the cluster centre, we obtain a slope of Gamma = -1.3. Closer in, the mass function of Westerlund 1 is shallower with Gamma = -0.6. The extrapolation of the mass function for stars with masses from 0.08 to 120 M_o yields an initial total stellar mass of ≈52 000 M_o, and a present-day mass of 20 000 to 45 000 M_o (about 10 times the stellar mass of the Orion nebula cluster, and 2 to 4 times the mass of the NGC 3603 young cluster), indicating that Westerlund 1 is the most massive starburst cluster identified to date in the Milky Way. Based on observations collected at the European Southern Observatory, La Silla, Chile, and retrieved from the ESO archive (Prog ID 67.C-0514).
Free 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
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2008A%26A...478..137... [ID No:1]