Many galaxies in the Universe have large spiral-shaped structures in flat disks. Those structures consist of gas and stars, many of whose properties are governed by processes involving magnetic fields. This project is a study of such structures in our own Milky Way galaxy using observations at near-infrared wavelengths. Catalogs containing thousands of times more detections than available previously will be produced for general astronomical use and released to the entire scientific community. Three graduate students will be trained in using various aspects of these data to study topics ranging from star formation in the Milky Way to comparing it to the properties of other nearby galaxies like our own.
The Galactic magnetic B-field has barely been characterized and its influence on the interstellar medium (ISM) is poorly known. Comprehensive analysis of the recently completed Galactic Plane Infrared Polarization Survey (GPIPS) data set will provide an important leap forward. This will include quantitative tests of models of the Galactic B-field in the disk as well as identifying the locations and natures of the regions in the disk now seen to exhibit strong departures from the general disk-parallel B-field alignment. Connecting what is seen in the GPIPS data for the Milky Way disk to large-scale B-fields in nearby edge-on galaxies will provide vital context as well as test whether the B-fields traced by synchrotron radio polarization, arising from hot plasma, connect smoothly to the B-fields in the cool, star-forming ISM. Deeper observations of important Galactic regions will answer B-field related questions with milli-parsec resolution in quiescent and star-forming sites and provide key tests of the two B-field model paradigms (strong vs weak fields). Studies resulting from using the Mimir instrument and from GPIPS provide vital B-field context, from the diffuse outer ISM layers of molecular clouds into the dense, core regions. New, K-band Mimir polarimetry of infrared dark clouds and well-known massive cloud core star formation regions will reach deep enough to provide context for the high column density zones observed with millimeter and submillimeter interferometric polarimetry.
GPIPS and Mimir data products have impact outside the study of B-fields in the ISM. Community use of GPIPS data will yield new findings on stars, stellar evolution, star clusters, and Galactic structure and assembly. Project support of GPIPS data products and software ensure their utility and legacy. The program of bringing undergraduate and graduate students to Arizona to operate Mimir on the Perkins telescope for class-based projects will continue and will include high school students participating in BU's RISE summer program. Though modest in numbers (~100 students in 8 years), these trips to the telescope have had profound personal and career impact on the students participating, be they from graduate or undergraduate observational classes or from the introductory, non-majors astronomy courses at BU. Public presentation opportunities at the Boston Museum of Science, BU Astronomy Department?s weekly open nights, and elsewhere will be actively pursued for this project. Finally, three graduate students will complete PhDs and several undergraduates and High School students will gain valuable research experience.
