Final Report Summary - GLOSTAR (A Global View of Star Formation in the Milky Way) Stars with more than about ten solar masses dominate galactic ecosystems and understanding the circumstances of their formation is one of the great challenges of modern astronomy. The spectacular HII regions they excite, delineate the spiral arms of galaxies such as our own, when seen face on – making it clear that star formation and Galactic structure are intimately related. The aim of this ERC Advanced Grant is to attain a Global View of Star Formation in the Milky Way in a powerful multipronged approach. GLOSTAR has produced impressive results: * Almost 100 Galactic star forming regions visible from the northern hemisphere have parallaxes measured by VLBI, approx. 70 of them by our team. We can already trace some of the spiral arms of the Milky Way, and measure their pitch angles – for the first time, (at least) part of our Galaxy reveals its true shape. Our preliminary results indicate that the combination of the IAU recommended values for the distance to the Galactic center, R_o, of 8.5 kpc and the circular rotation velocity at the position of the Sun, Theta_o, of 220 km/s is not consistent with our data, and that Theta_o probably needs to be revised to a value of ~245 km/s. * From our survey for submillimeter emission from cold, dense dust in the Milky Way, we obtained the locations and properties of unseen deeply embedded protostars and protoclusters. Complementary follow-ups of selected sources from the ATLASGAL submillimeter dust emission survey have also been obtained with the Plateau de Bure and the ALMA interferometers revealing the fragmentation and dynamics during the early phases of high-mass star formation. Most importantly, this data has been complemented with a comprehensive program to study is the radio wavelength (continuum and spectral line) signatures of star formation with a very sensitive survey of the Galactic plane accessible with the newly expanded Very Large Array, the Karl G. Jansky Very Large Array (JVLA). Our JVLA survey is in full swing with 90 square degrees that have been observed so far and further 42 square degrees that are already approved for observation. The data shows the uniqueness of the survey, reaching a sensitivity greatly surpassing previous centimeter surveys (by up to an order of magnitude!) and a spatial dynamical range, in particular in combination with data from the Effelsberg 100m single dish telescope, that rivals the results from infrared space missions. * We also study the infrared emission from more developed massive star clusters, deriving distance with the classic spectro-photometric method, properly calibrated with trigonometric parallaxes, and for the first time adapted to an extensive IR dataset. We analysed integral field spectrograph infrared data for a sample of clusters, amongst them those powering the key W31 and the W43 “mini”-starburst regions. In particular, we developed a novel and innovative method to categorize luminous stars by multi-mid infrared colour section criteria. We were awarded observing time on the ESO telescope and successfully collected the data, which are presently being reduced.Our synoptic approach has utilized Europe’s premier telescopes including ESO’s VLT, the European VLBI Network, the APEX telescope, and ALMA to create a coherent, unique dataset with true legacy value for a global perspective on star formation in our Galaxy.
