  The centre of NGC 4151 has been observed in the J-band with the SMIRFS
integral field unit (IFU) on the UK Infrared Telescope. A map of [Fe II]
emission is derived, and compared with the distributions of the optical narrow
line region and radio jet. We conclude that, because the [Fe II] emission is
associated more closely with the visible narrow-line region than with the radio
jet, it arises mainly through photoionization of gas by collimated X-rays from
the Seyfert nucleus. The velocity field and strength with respect to [Pa B] are
found to be consistent with this argument. The performance of the IFU is
considered briefly, and techniques for observation and data analysis are
discussed.
