Automated Kinematic Modelling of Warped Galaxy Discs in Large Hi
  Surveys: 3D Tilted Ring Fitting of HI Emission Cubes
  Kinematical parameterisations of disc galaxies, employing emission line
observations, are indispensable tools for studying the formation and evolution
of galaxies. Future large-scale HI surveys will resolve the discs of many
thousands of galaxies, allowing a statistical analysis of their disc and halo
kinematics, mass distribution and dark matter content. Here we present an
automated procedure which fits tilted-ring models to Hi data cubes of
individual, well-resolved galaxies. The method builds on the 3D Tilted Ring
Fitting Code (TiRiFiC) and is called FAT (Fully Automated TiRiFiC). To assess
the accuracy of the code we apply it to a set of 52 artificial galaxies and 25
real galaxies from the Local Volume HI Survey (LVHIS). Using LVHIS data, we
compare our 3D modelling to the 2D modelling methods DiskFit and rotcur. A
conservative result is that FAT accurately models the kinematics and the
morphologies of galaxies with an extent of eight beams across the major axis in
the inclination range 20$^{\circ}$-90$^{\circ}$ without the need for priors
such as disc inclination. When comparing to 2D methods we find that velocity
fields cannot be used to determine inclinations in galaxies that are marginally
resolved. We conclude that with the current code tilted-ring models can be
produced in a fully automated fashion. This will be essential for future HI
surveys, with the Square Kilometre Array and its pathfinders, which will allow
us to model the gas kinematics of many thousands of well-resolved galaxies.
Performance studies of FAT close to our conservative limits, as well as the
introduction of more parameterised models will open up the possibility to study
even less resolved galaxies.
