THE MILKY WAY AS A STAR FORMATION ENGINE

S. Molinari (INAF-IAPS, Rome, Italy),
J. Bally (University of Colorado, Boulder, United States),
J.-P. Bernard (IRAP, Toulouse, France),
S. Glover (Heidelberg University, ITA, Germany),
P. Martin (University of Toronto, Canada),
T. Moore (Liverpool John Moores University, United Kingdom),
A. Noriega-Crespo (IPAC-Caltech, Pasadena, United States),
R. Plume (University of Calgary, Canada),
L. Testi (ESO-HQ, Garching, Germany),
E. Vazquez-Semadeni (UNAM, Morelia, Mexico),
A. Zavagno (LAM, Marseille, France)

We review and discuss the latest observational scenario globally emerging from the latest generation of continuum and spectroscopic global-scale surveys of the mid-plane of the Galaxy from infrared to radio wavelengths, in terms of cloud formation and evolution, star and clump formation rate and efficiency throughout the Galaxy, evidence for density thresholds for the formation of protocluster-forming clumps, as well as the role of large-scale filamentary structures in channeling diffuse ISM into gravitationally bound clumps. The new view of the Milky Way thus assembled will be discussed in the context of competing theoretical frameworks distinguishing between "slow" and "fast" formation, outlining some of the challenges that this body of evidence poses to a variety of theoretical scenarios for large-scale star formation. We will review the most recent methods and evolutionary indicators used to classify the star formation activity in molecular clumps, comparing the different possible derivations of the local SFR and discussing its variation as a function of Galactocentric radius. The order-of-magnitude increase in the number of sources (mostly clumps) that are revealed in state-of-the-art infrared and submillimeter Galaxy-wide surveys make such studies possible with an unprecedented statistical significance. We will also review the present status of our understanding of the Galaxy as a global star formation engine in the context of similar studies in extragalactic systems, evaluating how the data on our own Galaxy compare with the proposed global star formation laws that relate properties of the interstellar medium to the star formation rate.

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