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J. D. P. Kenney (Yale U), J. van Gorkom (Columbia U), B. Vollmer (MPIfR Bonn)
A particularly clear example of ICM-ISM stripping in action is seen in the highly inclined Virgo cluster spiral galaxy NGC~4522, which has an undisturbed stellar disk and a selectively disturbed ISM. Recent imaging observations have shown extraplanar filaments of H\alpha-emitting gas arising from the edge of a truncated star forming disk. We present VLA HI and radio continuum images of NGC~4522, which reveal extraplanar neutral gas and a non-thermal radio plume with strikingly different distributions. The HI distribution is remarkably similar to the H\alpha distribution. In the plane of the stellar disk, the HI distribution is truncated beyond R=0.4R(25). Beyond this radius, the only HI is located above the disk plane. The extraplanar radio continuum emission is much more extended than the HI emission, forming a broad complex tail which stretches at least 3'=14 kpc from the galaxy center, clearly suggesting motion of the galaxy through the ICM. The limited extent of HI in the disk and the existence of secondary peaks in the projected HI surface density 30''=2.3 kpc above the disk plane might be explained by gas resettling into the galaxy in the aftermath of intense ram pressure stripping, as predicted by the simulations of Vollmer. While some properties of the ISM-ICM interaction may be understood via N-body sticky particle simulations, MHD simulations are clearly necessary for understanding the radio continuum tail.