Modeling Vertically Extended Neutral Gas in the Edge-on Galaxy NGC 4302

Recent realizations concerning kinematic measurements of gaseous halos in nearby galaxies may provide important clues to the origin of such halos and thereby the growth and evolution of galaxy disks. In particular, recent measurements have shown a decrease in rotation speed with height in a few halos, leading to various models which attempt to understand this gradient in terms of disk-halo flows and accretion of primordial gas. One observational issue is whether ionized and neutral halos show the same kinematics, suggesting a common origin or whether they diverge, leading to potentially different origins. The steepest gradient of rotation speed is -30 km/s/kpc in NGC 4302 (Heald et al. 2007), a galaxy with relatively weak star formation activity. Here we present deep VLA HI observations of this galaxy in the B and C configurations. From these observations, we clearly detect a vertically extended component. We present models showing whether the kinematics of this component are best represented by a flare, a warp along the line of sight, a lagging halo or a combination of the three. Due to asymmetries in the galaxy itself, these models vary somewhat between the approaching and receding halves. At this time we have successfully modeled a warp along the line of site and will have put constraints on any flare or lagging halo by the time of the meeting. Furthermore, we hope to complete analogous models of NGC 4244 in time for the meeting.