Axisymmetrical Gas Inflow in the Central Region of NGC 7331

Abstract

New Integral Field Spectroscopy of the central region of NGC 7331 reveals strong H$α$ emission in the well-known CO and HI ring of NGC 7331. The [NII]/H$α$ ratio indicates that a large scale stellar formation process is taken place at the ring in agreement with previous hypothesis about the exhaustion of gas in the inner to the ring region. The dynamics of stars and gas are not coupled. There is a ring of peculiar velocities in the ionized gas velocity map. These peculiar velocities can be well interpreted by the presence of an axisymmetric inflow of 40 km/s at the inner boundary of the large-scale gaseous ring. We infer an inwards total flux of 1.6 M$_{\odot}$yr$^{-1}$. This value is typical of the accretion rates in hypothetical {\bf large} nuclear black holes. Despite the large differences in the scales of the nucleus and the gas ring of NGC 7331, we suggest that this inwards flux is feeding the nucleus.