2015/05/11 by Maria Messineo, J. Simon Clark, Donald F. Figer +10
Chemistry · Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Fullerene Chemistry and Applications #Molecular cloud #Population #Red supergiant #Star cluster #Star formation #Stars #Stellar evolution #Stellar mass loss #Supergiant #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/805/2/110
ApJ (in press), 10 Figures
arxiv created 2015/05/11 · openalex publication_date 2015/05/27 · arxiv updated 2015/06/03 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Rich in H ii regions, giant molecular clouds are natural laboratories to study massive stars and sequential star formation. The Galactic star-forming complex W33 is located at and at a distance of 2.4 kpc and has a size of pc and a total mass of (0.8−8.0) M . The integrated radio and IR luminosity of W33—when combined with the direct detection of methanol masers, the protostellar object W33A, and the protocluster embedded within the radio source W33 main—mark the region as a site of vigorous ongoing star formation. In order to assess the long-term star formation history, we performed an infrared spectroscopic search for massive stars, detecting for the first time 14 early-type stars, including one WN6 star and four O4–7 stars. The distribution of spectral types suggests that this population formed during the past ∼2–4 Myr, while the absence of red supergiants precludes extensive star formation at ages 6–30 Myr. This activity appears distributed throughout the region and does not appear to have yielded the dense stellar clusters that characterize other star-forming complexes such as Carina and G305. Instead, we anticipate that W33 will eventually evolve into a loose stellar aggregate, with Cyg OB2 serving as a useful, albeit richer and more massive, comparator. Given recent distance estimates, and despite a remarkably similar stellar population, the rich cluster Cl 1813–178 located on the northwest edge of W33 does not appear to be physically associated with W33.