| Abstract | New 21cm \hIline observations of NGC 5204 are presented. A new method is discussed to model its severely warped \hI\ plane. Variations of 60(deg) in position angle and 20(deg) in inclination are needed to model this plane. The derived rotation curve extends out to ~ 13alpha (-1) . By combining this rotation curve with an optical (\pf) rotation curve derived in the first part of this study, a very well constrained mass model (best fit) is presented, with \M/L = 1.4 +/- 0.1 \mlo \ for the stellar disk and r_c = 2.7 +/- 0.1 kpc and sigma = 44.0 +/- 0.1 km s(-1) (rho_ z = 0.041 \M_sun pc(-3) ) for the dark isothermal halo. The stellar disk, although dynamically more important than the \hI, is only a minor contributor to the overall potential. Contrary to what is seen in more massive spirals, the dark halo has a significant contribution even within the optical radius. Many characteristics of the mass distribution place NGC 5204, a magellanic spiral, closer to dwarf irregulars than to bright spirals. |
