Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1B042

W3 Main, a test case for cluster formation

Bik, Arjan (Max Planck Institute for Astronomy, Heidelberg)

Embedded clusters play an important role in the star formation process: it is in these embedded clusters where most, or even all, young stars are born. In such star-forming regions, stars interact via stellar feedback and dynamical interactions with each other and with the surrounding interstellar medium. Therefore, the understanding of the physical processes operating on scales of a few tens of parsecs becomes fundamental to perceive the impact of star formation on global galactic scales. We use the embedded cluster W3 Main as a test case to derive constraints on the formation of embedded clusters. Deep near-infrared JHK imaging of W3 Main as well as K-band spectroscopy of the massive stars using LUCI1 at the LBT provide us with a detailed picture of this complex region. We combine these data with a large multi-wavelength dataset, ranging from X-rays to radio in order to derive its formation history. Based on the spectroscopy of the massive stars and the presence of hyper-compact HII regions in W3 Main we derive an age spread of 2 -3 Myrs for W3 Main. This age spread is comfirmed by a spatially varying disk fraction of the low-mass stars. The age of the most massive O star IRS2, and the nature of the HII regions suggest that star formation in W3 Main started at least 2-3 Myrs ago, and due to dynamical interactions with dense molecular cores in the surroundings and possible internal triggering, star formation is continuing until the present day. Currently the youngest population is located in the center and may be the latest dense concentration of molecular gas in the contracting cloud, forming the youngest sub cluster around IRS5.

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