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Is the massive star cluster Westerlund 2 double? - A high resolution multi-band survey with the Hubble Space Telescope

Published online by Cambridge University Press:  31 March 2017

Peter Zeidler ,
Antonella Nota ,
Elena Sabbi ,
Eva K. Grebel ,
Monica Tosi ,
Alceste Z. Bonanos ,
Anna Pasquali ,
Carol Christian  and
Selma E. de Mink
Peter Zeidler
Affiliation:
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany email: pzeidler@ari.uni-heidelberg.de Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Antonella Nota
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA ESA, SRE Operations Devision
Elena Sabbi
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Eva K. Grebel
Affiliation:
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany email: pzeidler@ari.uni-heidelberg.de
Monica Tosi
Affiliation:
INAF - Osservatorio Astronomico di Bologna
Alceste Z. Bonanos
Affiliation:
IAASARS, National Observatory of Athens, GR-15326 Penteli, Greece
Anna Pasquali
Affiliation:
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany email: pzeidler@ari.uni-heidelberg.de
Carol Christian
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Selma E. de Mink
Affiliation:
Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands
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Abstract

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Westerlund 2 (Wd2) is one of the most massive young star clusters known in the Milky Way. The close proximity (4.16 kpc) to the Sun, and the young age (2.0 Myr) allow us to study star formation in detail at a high spatial resolution. We present results from our recent deep multi-band survey in the optical and near-infrared obtained with the Hubble Space Telescope. We demonstrated that, as expected, the region is affected by significant differential reddening with a median value of E(B − V)g = 1.87 mag. The distance was inferred from the dereddened color-magnitude diagrams using Padova isochrones. Analyzing the spatial distribution of stars we found that Wd2 consists of two sub-clumps, namely the main cluster of Westerlund 2 and a less well populated clump located to the North. We estimated the same age of 0.1–2.0 Myr for both sub-clumps, thus we conclude that they are likely coeval.

Keywords

techniques: photometric - stars: early type - stars: pre-main sequence - HII regions - open clusters and associations: individual (Westerlund 2) - infrared: stars
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S316: Formation, evolution, and survival of massive star clusters , August 2015 , pp. 55 - 60
Copyright
Copyright © International Astronomical Union 2017 

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