This work combines new observations of NIR starlight linear polarimetry with previously simulated observations in order to constrain dynamo models of the Galactic magnetic field .
Polarimetric observations were obtained with the Mimir instrument on the Perkins Telescope in Flagstaff , AZ , along a line of constant Galactic longitude ( \ell = 150 \arcdeg ) with 17 pointings of the 10 \arcmin \times 10 \arcmin field of view between -75 \arcdeg < b < 10 \arcdeg , with more frequent pointings towards the Galactic midplane .
A total of 10,962 stars were photometrically measured and 1,116 had usable polarizations .
The observed distribution of polarization position angles with Galactic latitude and the cumulative distribution function of the measured polarizations are compared to predicted values .
While the predictions lack the effects of turbulence and are therefore idealized , this comparison allows significant rejection of A0-type magnetic field models .
S0 and disk-even halo-odd magnetic field geometries are also rejected by the observations , but at lower significance .
New predictions of spiral-type , axisymmetric magnetic fields , when combined with these new NIR observations , constrain the Galactic magnetic field spiral pitch angle to -6 \arcdeg \pm 2 \arcdeg .