The distance to the young open cluster Westerlund 2

TL;DR

This paper estimates the distance to the young star cluster Westerlund 2 at approximately 3.0 kpc, using new photometry, spectral classifications, and analysis of dust extinction properties.

Contribution

It provides a revised distance measurement to Westerlund 2 based on new photometric data and an analysis of the anomalous dust extinction law in its direction.

Findings

Distance to Westerlund 2 is about 3.0 kpc.

Dust extinction law in Carina is anomalous with R_V~3.8.

Method combines variable-extinction and color excess techniques.

Abstract

Evidence is presented indicating that the young star cluster Westerlund~2 lies $d_{\odot}\sim3.0$ kpc in the direction of Carina. The distance is tied partly to new $UBVRI_c$ photometry and revised spectral classifications for cluster stars, which imply that dust in the direction of Carina is characterized by an anomalous extinction law ($R_V\sim3.8$). That result was determined from a multi-faceted approach relying on the variable-extinction and color excess methods.