Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters

Abstract

We report the results of Australia Telescope Compact Array (ATCA) observations of the Westerlund~1 (Wd1) region in the SiO v=1, J=1-0 and H2O 6(16)-5(23) maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with 6 massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v=1, J=1-0 and H2O 6(16)-5(23) maser lines are detected toward 2 of 4 known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F21/F12) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in 6 massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H2O line tend to distribute in a region with large L values.

52 pages, 11 figures, 15 tables; accepted for publication in ApJ; full resolution version is available from http://web.hku.hk/~junichi/paper/fok_etal_atca-Wd1.pdf

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Cited by in corpus (10)

• The Age of Westerlund 1 Revisited
• An ALMA 3mm continuum census of Westerlund 1
• The Ionized Nebula surrounding the Red Supergiant W26 in Westerlund 1
• A VLT/FLAMES survey for massive binaries in Westerlund 1: VIII. Binary Systems and Orbital Parameters
• Searching for Cool Dust: II. Infrared Imaging of the OH/IR Supergiants, NML Cyg, VX Sgr, S Per and the Normal Red Supergiants RS Per and T Per
• Maser and Infrared Studies of Oxygen-Rich Late/Post-AGB Stars and Water Fountains: Development of a New Identification Method
• Cold gas in hot star clusters: the wind from the red supergiant W26 in Westerlund 1
• Wide Field CO Mapping in the Region of IRAS 19312+1950
• Radio Stars and Their Lives in the Galaxy
• A cosmic-ray loaded nascent outflow driven by a massive star cluster