Volume 515, June 2010
|Number of page(s)||24|
|Published online||09 June 2010|
The dark matter halo shape of edge-on disk galaxies
II. Modelling the HI observations: methods
Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Cotter Road, ACT 2611, Australia e-mail: email@example.com; firstname.lastname@example.org
2 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: email@example.com
Accepted: 9 March 2010
This is the second paper of a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. For this purpose, we observe the Hi in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. To calculate the force fields, we need to analyse the observed XV diagrams to accurately measure all three functions that describe the planar kinematics and distribution of a galaxy: the radial Hi surface density, the rotation curve and the Hi velocity dispersion. In this paper, we discuss the improvements and limitations of the methods previously used to measure these Hi properties. We extend the constant velocity dispersion method to include determination of the Hi velocity dispersion as a function of galactocentric radius and perform extensive tests on the quality of the fits. We will apply this “radial decomposition XV modelling method” to our Hi observations of 8 Hi rich, late-type, edge-on galaxies in the third paper of this series.
Key words: galaxies: structure / galaxies: kinematics and dynamics / galaxies: halos / galaxies: ISM
© ESO, 2010
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