NGC-5204 - A STRONGLY WARPED MAGELLANIC SPIRAL .1. LIGHT-DISTRIBUTIONAND H-II KINEMATICS

BVRI surface photometry and Fabry-Phot (H alpha) 2D spectroscopy of th e Magellanic-type spiral NGC 5204 are presented. While its surface bri ghtness is typical of a normal spiral, with B-c(0)=21.60 mag arcsec(-2 ) NGC 5204 is clearly a small system with an exponential scale length alpha(-1)=0.8 kpc. The H alpha velocity field is modeled with an axisy mmetrical field, using the orientation parameters derived from the pho tometry. A mass model with M/L=1.8 M(.)/L(B.) for the stellar disk can account for the circular velocities V-C(R) only out to 1.2 alpha(-1) (0.2R(Ho)). This shows that, contrary to what is seen in more massive spirals where the dark halo has an important contribution mainly in th e outer parts, the dark component of this low mass system contributes a significant amount to the mass, even in the inner parts. (C) 1996 Am erican Astronomical Society.