Star Formation in the W49A Molecular Cloud: Birth of a Massive Star Cluster

N. L. Homeier, J. Alves

The W49A star-forming region is embedded in a 106

M⊙ molecular cloud, one of the most massive in our

Galaxy. It has been long known as one of the most luminous radio H II

regions, containing 30-40 compact and ultracompact H II regions and

several hot cores. We have detected a previously unknown massive star

cluster (Cluster 1) embedded in the W49 molecular cloud using JHKs

observations with SOFI+NTT. We find that the inferred mass of Cluster 1

is 1-2 × 104 M⊙, and is 2 pc in

projected distance from the largest grouping of ultracompact H II

regions (including the Welch ring). We use the extensive line-of-sight

extinction to isolate a population of objects associated with W49A, and

use this sample to obtain a mass function. The slope of the derived mass

function for objects associated with W49A, -1.3 ± 0.3, is

consistent with a Salpeter slope. About 3 pc away from the main

star-forming complexes seen in near-infrared and radio observations is

an ˜ 80 M⊙ star ionizing a compact H II region

(object CC). We obtained adaptive optics imaging with NACO on the VLT of

the 1.5 pc surrounding this object to search investigate the stellar

initial mass function in the vicinity of a massive star. On the global

molecular cloud scale in W49, massive star formation apparently did not

proceed in a single concentrated burst, but in small groups, or


External organisation(s)
Johns Hopkins University, European Southern Observatory (Germany)
Publication date
Austrian Fields of Science 2012
103004 Astrophysics
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