The galaxy M51 was observed using the Mimir instrument on the Perkins telescope to constrain the resolved H-band ( 1.6 \mu m ) polarization across the galaxy .
These observations place an upper limit of P _ { H } < 0.05 \% on the H -band polarization across the face of M51 , at 0.6 arcsecond pixel sampling .
Even with smoothing to coarser angular resolutions , to reduce polarization uncertainty , the H -band polarization remains undetected .
The polarization upper limit at H -band , when combined with previous resolved optical polarimetry , rules out a Serkowski-like polarization dependence on wavelength .
Other polarization mechanisms can not account for the observed polarization ratio ( P _ { H } / P { VRI } \lesssim 0.05 ) across the face of M51 .