On the Distance and Molecular Environment of Westerlund 2 and HESS J1023-575

Abstract

The extended TeV gamma-ray source HESS J1023-575 is coincident with the massive, young stellar cluster Westerlund 2 (Wd2) and its surrounding HII region RCW 49. On the basis of an analysis of the CO emission and 21 cm absorption along the line of sight to Wd2, it is argued that this cluster, and by assumption the TeV source as well, must be associated with a giant molecular cloud in the far side of the Carina arm with a mass of 7.5 x 10^5 Mo. Analysis of the spatial and velocity structure of the cloud reveals clear evidence of interaction with Wd2. The cloud's kinematic distance of 6.0 +/- 1.0 kpc is shown to be consistent with distances inferred both from the radius-linewidth relation of molecular clouds and from the foreground gas column derived from 230 X-ray sources in Wd2.

ApJ Letter, accepted July 5, 2007. 10 pages, 4 figures (2 color)

References in corpus (1)

• Detection of extended very-high-energy gamma-ray emission towards the young stellar cluster Westerlund 2

Cited by in corpus (15)

• Molecular clouds towards RCW 49 and Westerlund 2; Evidence for cluster formation triggered by cloud-cloud collision
• Cloud-cloud collisions and triggered star formation
• Fermi-LAT Search for Pulsar Wind Nebulae around gamma-ray Pulsars
• Interstellar Weather Vanes: GLIMPSE Mid-Infrared Stellar-Wind Bowshocks in M17 and RCW49
• Chandra monitoring of the very massive binary WR20a and the young massive cluster Westerlund2
• The Villafranca catalog of Galactic OB groups: I. Systems with O2-O3.5 stars
• The deep OB star population in Carina from the VST Photometric H$\alpha$ Survey (VPHAS+)
• Reddening, Distance, and Stellar Content of the Young Open Cluster Westerlund 2
• A High-Resolution Multiband Survey of Westerlund 2 With the Hubble Space Telescope. III. The present-day stellar mass function
• New OB star candidates in the Carina Arm around Westerlund 2 from VPHAS+
• Using Interstellar Clouds to Search for Galactic PeVatrons: Gamma-ray Signatures from Supernova Remnants
• Proper motions of OB stars in the far Carina Arm
• Warm Ionized Medium Throughout the Sagittarius-Carina Arm
• Probing the hadronic nature of the gamma-ray emission associated with Westerlund 2
• The Molecular Environment of the Gamma-ray Source TeV J2032+4130