NGC 5775 and NGC 2613 - On high latitude HI and lagging halos

The edge-on galaxies, NGC 5775 and NGC 2613, show discrete Hi features which span the disk-halo interface, in some cases to very high z (up to 21 kpc). NGC 5775 shows evidence for a lagging halo up to 5 to 6 kpc from the plane; however, such a lag is not obvious in NGC 2613, possibly due to its lower inclination. If the H I feature survives to very high latitude, a velocity gradient is no longer observed, suggesting that the feature emerges from the disk-halo transition region into a different environment. In this regime, some of the features break up into many clumps over a wide velocity range similar to Population 11 dynamics. Thus, discrete H I features may be used as probes of the disk-halo interface.