Galaxy discs as accretion discs

Abstract

Accretion and accretion discs around compact objects such as black holes and neutron stars are well studied phenomena, but galactic discs have rarely been examined as accretion discs, despite showing clear evidence of radial mass inflow. Rotation curves, radial velocity and radial mass flux data for ten different spiral galaxies were acquired from Schmidt et al. (2016) who in turn were working with data from The HI Nearby Galaxy Survey (THINGS). The data are used to calculate several quantities which are essential for accurately modelling accretion discs, with a focus on two different versions of the parameter, which describes the efficiency with which turbulence acts as a source of "effective" viscosity in the accretion process. These quantities are then analysed with consideration for the properties of the galaxies and the structures present. While there was no obvious connection found between the value of and the spiral structure present throughout the disc structures with clearer radial limits such as rings and bars were found to have definite effects on the value of .