Spectropolarimetric studies of Sgr A West at 10μm reveal intrinsically polarized emission from the northern arm. The polarization, of amount 7–8 %, is attributed to emission from dust grains which are aligned by a magnetic field directed along the line of the northern arm. Along the eastern arm the polarization is smaller and indicates either a weaker field or one directed closer to the line of sight.
Polarized emission has also been observed at 100 μm from aligned grains in the ring of molecular gas which apparently encircles Sgr A. The aligning magnetic field lies in the plane of the ring and is probably toroidal. The correspondence between the polarization position angles at 10 and 100 μm suggests a model in which the northern arm is a disrupted filament from the molecular ring.
While the uncertain magnetic properties of grains prevent a reliable direct estimate of field strength, circumstantial evidence suggests it is larger than elsewhere in the Galaxy and possibly large enough to influence the dynamics of the region.