amount of total extinction: A$_B\leq$0.5 mag. We therefore checked for the presence of color-dependent extinction by studying the distribution of the (U–R$_C$) color index in one square degree areas over the central part of the Virgo cluster. The data used for this test, and an extensive description of the method and results, are given in the Appendix to this paper. Here we emphasize that the results show that the galaxies in the direction of the Virgo Ring (VR) part with the lowest FIR emission appear slightly bluer than those in the direction of the two regions with higher FIR emission. The difference is significant to $\geq$95%. Interpreted as dust extinction, this difference in average (U–R$_C$) color index indicates a possible wavelength-dependent extinction of $\Delta$(U–R$_C$)$\simeq$0.3 mag between areas with high FIR emission and areas with less dust, a total extinction A$_V\simeq$0.33 for a typical Milky Way extinction law, although this was not checked here.

Radio information
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Here we show that X-ray observations of the region indicate a two-component makeup for the hot gas, and that the morphology and kinematics of the HI are peculiar. Böhringer (1995) mapped the X-ray emission from the immediate vicinity of M87; this is the region 