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We report the results of high spatial and spectral resolution integral-fieldspectroscopy of the central ~3 x 3 arcsec^2 of the active galaxy NGC 1275(Perseus A), based on observations with the Near-infrared Integral FieldSpectrograph (NIFS) and the ALTAIR adaptive-optics system on the Gemini Northtelescope. The circum-nuclear disc in the inner R~50 pc of NGC 1275 is seen inboth the H2 and [FeII] lines. The disc is interpreted as the outer part of acollisionally-excited turbulent accretion disc. The kinematic major axis of thedisc at a position angle of 68 deg is oriented perpendicular to the radio jet.A streamer-like feature to the south-west of the disc, detected in H2 but notin [FeII], is discussed as one of possibly several molecular streamers,presumably falling into the nuclear region. Indications of an ionizationstructure within the disc are deduced from the HeI and Br gamma emission lines,which may partially originate from the inner portions of the accretion disc.The kinematics of these two lines agrees with the signature of thecircum-nuclear disc, but both lines display a larger central velocitydispersion than the H2 line. The rovibrational H2 transitions from the core ofNGC 1275 are indicative of thermal excitation caused by shocks and agree withexcitation temperatures of ~1360 and ~4290 K for the lower- and higher-energyH2 transitions, respectively. The data suggest X-ray heating as the dominantexcitation mechanism of [FeII] emission in the core, while fast shocks are apossible alternative. The [FeII] lines indicate an electron density of ~4000cm^{-3}. The H2 disc is modelled using simulated NIFS data cubes of H2 emissionfrom inclined discs in Keplerian rotation around a central mass. Assuming adisc inclination of 45 deg +/- 10 deg, the best-fitting models imply a centralmass of (8^{+7}_{-2}) x 10^8 Msun. (abridged)

Kinematics and Excitation of the Molecular Hydrogen Accretion Disc in NGC 1275