Trigonometric parallaxes of massive star forming regions: G012.88+0.48 and W33

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: kimmer@mpifr-bonn.mpg.de
² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, 02140 Cambridge, MA, USA

Received: 26 November 2012
Accepted: 25 March 2013

Abstract

We report trigonometric parallaxes for water masers in the G012.88+0.48 region and in the massive star forming complex W33 (containing G012.68−0.18, G012.81−0.19, G012.90−0.24, G012.90−0.26), from the Bar and Spiral Structure Legacy (BeSSeL) survey using the Very Long Baseline Array. The parallax distances to all these masers are consistent with $\mathrm{2.4}{\mathrm{0}}_{-0.15}^{\mathrm{+}\mathrm{0.17}}$ kpc, which locates the W33 complex and G012.88+0.48 in the Scutum spiral arm. Our results show that W33 is a single star forming complex at about two-thirds the kinematic distance of 3.7 kpc. The luminosity and mass of this region, based on the kinematic distance, have therefore been overestimated by more than a factor of two. The spectral types in the star cluster in W33 Main have to be changed by 1.5 points to later types.