NGC-5204 - A STRONGLY WARPED MAGELLANIC SPIRAL .2. H-I KINEMATICS ANDMASS-DISTRIBUTION

New 21 cm H I line observations of NGC 5204 are presented. A new metho d is discussed to model its severely warped H I plane. Variations of 6 0 degrees in position angle and 20 degrees in inclination are needed t o model this plane. The derived rotation curve extends out to similar to 13 alpha-1. By combining this rotation curve with an optical (Fabry -Perot) 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 M./L(B). for the stellar disk and r(c) = 2.7 +/- 0.1 kpc and si gma = 44.0 +/- 0.1 km s(-1) (rho(0) = 0.041M. pc(-3)) for the dark iso thermal halo. The stellar disk, although dynamically more important th an the HI, is only a minor contributor to the overall potential. Contr ary to what is seen in more massive spirals, the dark halo has a signi ficant contribution even within the optical radius. Many characteristi cs of the mass distribution place NGC 5204, a magellanic spiral, close r to dwarf irregulars than to bright spirals. (C) 1997 American Astron omical Society.