Abstract. We present new stellar kinematical profiles of four galaxy hosts of active galactic nuclei, using the 12 CO bandhead around 2.3 µm with the ISAAC/VLT spectrograph. We find that the nuclear bars or discs, embedded in large-scale primary bars, have all a decoupled kinematics, in the sense that the maximum of the rotational velocity occurs in the nuclear region. In three cases (NGC 1097, NGC 1808 and NGC 5728), the velocity dispersion displays a significant drop at the nucleus, a rarely observed phenomenon. We also detect kinematical asymmetries (m = 1 mode) along the nuclear bar major-axis of NGC 1808 and NGC 5728, dynamical counterparts of corresponding asymmetries in the surface brightness. We have derived simple dynamical models in an attempt to fit the kinematics of each galaxy and reconstruct the full velocity field. For all four targets, the fits are good, and confirm the presence of the decoupled nuclear components. These models cannot however reproduce the observed central drop in the dispersion. We suggest that this drop is due to a transient cold nuclear disc, fuelled by gas inflow along the bar, that has recently formed new stars.

Abstract. Surface photometry in the J and K bands of 15 southern Seyfert or starburst galaxies is presented. The detailed central morphology and structural properties of these objects were analyzed by fitting ellipses to isophotes. New central peculiar structures have been identified like, for instance, three double-barred systems (ESO 215-G031; ESO 320-G030; ESO 443-G017), one object with a nested nuclear spiral structure at the center of a primary bar (NGC 5135), one object with a nuclear bar without evidence of a large-scale bar (NGC 4941), and one galaxy with a likely dissolved secondary bar within a primary one (ESO 508-G005). The J − K radial profile proved to be reasonably well linked with the presence of a starburst, but not with the Seyfert activity. For significant starbursts, the central J −K value is 0.3 − 1.5 magnitude larger than the disc one.

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