Research WP5

Galaxy Structure and Kinematics - Rotation Curves and the Tully-Fisher Relation.

Gas-rich galaxies afford the opportunity to derive their gravitational potentials with high accuracy, based on a detailed analysis of the kinematics of the atomic hydrogen gas disks that often extend far into the dark matter halo. The gravitational force is build up by the main structural components of a galaxy such as its stellar and gaseous disks, its central bulge and the elusive dark matter halo. The S4G data allows for an accurate assessment of the distribution of the stars in such galaxies while the distribution of the gas is derived from high-quality 21cm spectral-line interferometric aperture synthesis imaging obtained with the WSRT, VLA and GMRT radio telescopes, supplemented by H-alpha Fabry-Perot observations using the GHaFaS instrument on the 4.2m William Herschel Telescope.

The goal of this work package is to construct and decompose high-quality composite (HI+Ha) rotation curves into the relative contributions by the main structural components mentioned above. This will provide insights in the distributions of the visible and dark matter in galaxies. Furthermore, the high-quality rotation curves will allow to refine the Tully-Fisher relation by identifying the relevant kinematic measure, investigating how the statistical properties of the Tully-Fisher relation depend on the used photometric bands, and studying whether the residuals correlate with other global properties of the galaxies such as surface brightness, disk scale lengths, star formation rates, the presence of a bar, warp or other nearby galaxies.