Measurements of Magnetic Field Strengths in the Galaxy

Dr. Thomas Troland, at the University of Kentucky, will carry out an observational program to determine magnetic field strengths in our Galaxy and slightly beyond. Using the radio frequency Zeeman effect, Dr. Troland and collaborators will measure field strengths in the diffuse neutral hydrogen (HI) gas, in the interclump medium of giant molecular clouds (GMCs), in molecular cores, and in very dense post-shock regions associated with massive star formation. These measurements will cover a wide density range, and they will help answer a number of important questions. For example, what is the range of Alfvenic Mach numbers in the diffuse interstellar medium (ISM)? How do field strengths scale with gas density among the two main components of the diffuse gas? How strong is the magnetic field in high velocity clouds (HVCs)? Are static fields strong enough to provide long term support to GMCs given recent theoretical studies suggesting magneto-hydrodynamic (MHD) turbulence is short-lived? Are static fields strong enough to provide support for molecular cores, and how does the field strength scale with gas density within them? What is the role of magnetic fields in the post-shock outflow regions probed by H2O masers, and how coherent are these fields among maser spots? In many cases, answers to these questions are emerging, but data are still so sparse that it is impossible to draw well-founded conclusions. To carry out this program, Dr. Troland will make use of established radio astronomy instruments as well as new ones. The most prominent new instrument is the Green Bank Telescope (GBT). Expressly designed for ultra-low sidelobe response, this telescope should have a profound effect upon Zeeman effect studies of the magnetic field. Dr. Troland will also use the Arecibo telescope and possibly the IRAM 30m telescope as a part of this program. New instrumental capabilities are complemented by growing theoretical capabilities for numerical simulation of MHD. Advances on both the observational and theoretical fronts in the next few years are likely to significantly increase our understanding of interstellar magnetic phenomena. This research program will involve graduate education at the University of Kentucky. It will also involve collaboration with a new regional colleague (and former graduate student) Dr. Anuj Sarma of Eastern Kentucky University. EKU is an undergraduate institution with an interest in bringing research experiences to its students. Sarma's participation in the research program will not only be important for the science output, it will also help him establish a research program at his own institution. ***