Formation of Galactic Massive Stars and Star Clusters

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This work builds upon the Bolocam Galactic Plane Survey (BGPS) for which the principal investigator had previous support from the NSF. Now the most massive proto-cluster clumps found in that survey are investigated with advanced observational facilities at the highest possible angular resolution from near-infrared through cm-wavelengths These observations are used to learn how massive stars and clusters form in the Milky Way as well as in other galaxies. Understanding the formation of massive stars is a necessary piece in a complete picture of galactic structure and evolution. The knowledge about massive stars is also important in other areas of astronomy, e.g., these stars produce heavy elements through nucleosynthesis, and they play a role in the growth of Active Galactic Nuclei. Two major mechanisms have been proposed for massive star formation: Competitive accretion from a cluster of interacting clumps and isolated collapse of massive cores in a high pressure environment. In this work it is addressed if massive stars form as isolated systems, or if they interact with sibling stars and compete to accrete from their parent clump. This work also leads to a better understanding of the role of feedback such as outflows and UV radiation on subsequent star formation in the clump. Other questions addressed by this work are what determines the number of stars formed and the upper stellar mass-limit, and what conditions lead to unbound OB associations versus gravitationally bound clusters.The observations target the Galaxy's most massive star-forming regions at high spatial resolution and will use the Apache Point Observatory (APO), the Expanded Very Large Array (EVLA), the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), the Atacama Large Millimeter Array (ALMA) and adaptive optics on telescopes such as Gemini. A large amount of data is already available and a significant part of the program is for new observations with the most advanced instruments and telescopes. Several of these instruments have been developed with funding from the NSF. The target list includes the two nearest active, high-luminosity sources, Orion A and Cepheus A, where several of the observing methods have been demonstrated and evidence of significant dynamical interactions has been discovered.This project involves a large team of researchers which strengthens the academic network infrastructure. Two graduate students work on their doctoral theses as part of this project, and there are opportunities for more graduate- and undergraduate student participation. The graduate students will also be actively involved in the outreach activities.A s part of this work the principal investigator implements an undergraduate research program at Sommer-Bausch Observatory (SBO) in Boulder. This introduces physics and astronomy undergraduate students from the University of Colorado to photometric monitoring of young stars in the closest star-forming regions that are sufficiently un-obscured to permit observations at visual wavelengths with the 24" SBO telescope. Stunning images are expected from this project which find use in popular talks at Fiske Planetarium and the Denver Museum of Nature and Science, and which are to be disseminated via the internet and Fiske planetarium.