NGC 1566: Spectroscopy of a symmetric system with Seyfert nucleus

Abstract

The central region and main body of the very symmetrical galaxy NGC1566 were observed and studied spectrophotometrically and kinematically. We found that: a) the total masses derived from the Satoh model fitted to the rotation curve, and from the global Hi radial velocity profile, are coincident: 2 × 10 11 M⊙, which implies the presence of two galactic subsystems without the need for a massive halo; b) from the rotation curve of the fitted model an outflow motion at the bar tips is confirmed (ΔV ∼ 40kms -1); c) the observed non-circular motions in some regions with significant blue shifts (ΔV ∼ 60kms -1) would represent inflows of gas to the nucleus; d) the fitted pattern speed at (23 ± 2)kms -1 kpc -1 allows one to explain the radial positions of the inner ring, the star formation ridge of the arms, and the ring at the main disk outer edge, as result of dynamical resonances; e) the nucleus was in a stage of Seyfert 1.8 and in a low level of activity during observations; f) nuclear and inner rings were detected; there is also evidence of a ring at the main disk outer edge; g) some emission regions in the arms have Hα fluxes higher than in the nucleus; h) the star bursts in the ring at the bar end radius would be younger than in the arms; i) the Hα emission appears to be correlated with the thermal component of the continuum radiation and with the molecular gas over the whole galaxy.