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arXiv · 1608.05559

The Shape of Dark Matter Haloes III. Kinematics and Structure of the HI disc

S. P. C. Peters·P. C. van der Kruit·R. J. Allen·K. C. Freeman
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Abstract

We present a new strategy for fitting the structure and kinematics of the HI in edge-on galaxies using a fit to the terminal-velocity channel maps of a HI data cube. The strategy can deal with self-absorbing HI gas and the presence of warps. The method is first tested on a series of models. We demonstrate that fitting optically thin models to real galaxies will lead to an overestimation of the thickness and velocity dispersion, and to a serious underestimation of the HI face-on column densities. We subsequently fit both self-absorption and optically thin models to the HI data of six edge-on galaxies. In three of these we have also measured the velocity dispersion. On average 27 \pm 6 % of the total HI mass of edge-on galaxies is hidden by self-absorption. This implies that the HI mass, thickness and velocity dispersion of galaxies is typically underestimated in the literature.

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S. P. C. Peters, P. C. van der Kruit, R. J. Allen, K. C. Freeman. 2016-08-19. The Shape of Dark Matter Haloes III. Kinematics and Structure of the HI disc. https://doi.org/10.1093/mnras%2Fstw1854

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