2015ApJ...808..153Z

NGC 4013 is a distinctly warped galaxy with evidence of disk-halo activity. Through deep H i observations and modeling we confirm that the H i disk is thin (central exponential scale height with an upper limit of 4" or 280 pc), but flaring. We detect a vertical gradient in rotation velocity (lag), which shallows radially from a value of -35_–28⁺⁷ km/s/kpc at 1.'4 (5.8 kpc), to a value of zero near R₂₅(11.2 kpc). Over much of this radial range, the lag is relatively steep. Both the steepness and the radial shallowing are consistent with recent determinations for a number of edge-ons, which have been difficult to explain. We briefly consider the lag measured in NGC 4013 in the context of this larger sample and theoretical models, further illuminating disk-halo flows.