A Galaxy-wide characterization of the role of magnetic field in star formation with large-scale far-infrared polarimetric mapping: the role of the BLAST Observatory
The latest generation of Herschel Galactic surveys revealed that most dense clumps and cores in all evolutionary stages are found in association with large-scale filamentary structures, and available polarization observations show that magnetic fields B have a crucial role in their assembly and fragmentation process into dense star-forming clumps and cores. Yet the extent to which B really contributes to drive or to slow-down the collapse and fragmentation of star forming clouds is still an open question that needs to be addressed in a systematic and statistically significant fashion to get a full picture of the star-formation mechanism. Hundreds-square-degree polarimetric mapping of Galactic Star-forming regions at sub-arcmin resolution in the Far Infrared is the key-observable capable of delivering this picture. In a coherent 2-tiered approach we will first study the intensity and morphology of magnetic fields in great detail by polarimetric mapping of nearby star-forming complexes in their entirety. We will then generalise our understanding to the entire Galaxy with polarimetric imaging of hundreds of large-scale filamentary molecular clouds toward both the inner and outer Galactic Plane, to map the role of B across the full diversity of physical and environmental conditions in which star formation takes place in the Milky Way. Fully complementary to SOFIA, the BLAST Observatory is a proposed balloon-borne 1.8 meter off-axis telescope that will map linearly polarized dust emission at 175, 250 and 350 microns. Operating at more than 30km altitude (>99.5% of the Earth’s atmosphere) from an ultra-long duration stratospheric balloon platform the BLAST Observatory will be the unique facility to create high-sensitivity large-area (hundreds of deg^2), detailed (best resolution 28’’) maps of magnetic fields. Ancillary information from Herschel Gould Belt and Hi-GAL surveys, augmented with multiwavelength large-scale IR-radio surveys in continuum and molecular lines, will provide the essential toolkit to relate the properties of magnetic fields to the physical and evolutionary stage of fragmenting structures down to the core scale, and eventually the rate and efficiency with which stars form. About 30% of the observing time will be open to competitive proposals from the larger community. The data provided by BLAST Obs will be a great legacy for follow-up projects with SOFIA to map, e.g., physical properties of the warm and shocked gas in star-forming sites with fully characterised B-field properties.