Hierarchical Triggering of Star Formation by Superbubbles in W3/W4
M.S. Oey, A.M. Watson, K. Kern, & G.L. Walth
It is generally believed that expanding superbubbles and mechanical
feedback from massive stars trigger star formation, because there are
numerous examples of superbubbles showing secondary star formation at
their edges. However, while these systems show an age sequence, they
do not provide strong evidence of a causal relationship. The W3/W4
Galactic star-forming complex suggests a three-generation hierarchy:
the supergiant shell structures correspond to the oldest
generation; these triggered the formation of IC 1795 in W3, the
progenitor of a molecular superbubble; which in turn triggered the
current star-forming episodes in the embedded regions W3-North,
W3-Main, and W3-OH. We present UBV photometry and spectroscopic
classifications for IC 1795, which show an age of 3 - 5 Myr. This
age is intermediate between the reported 6 - 20 Myr age of the
supergiant shell system, and the extremely young ages
(10^4 - 10^5 yr) for the embedded knots of ultracompact HII
regions, W3-North, W3-Main, and W3-OH.
Thus, an age sequence is indeed confirmed for the entire W3/W4
hierarchical system. This therefore provides some of the first
convincing evidence that superbubble action and mechanical feedback are
indeed a triggering mechanism for star formation.
AJ, 129, 393
Table of Contents
Journal article via ADS
astro-ph/0501136
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Figure 2: Grayscale of W3 region from the DSS, overlaid by CO contours from
the FCRAO CO survey.
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