the underlying continuum [see Fig.5 of @Laurent2000]. The closer f$_{6.7\mu m}$/f$_{6\mu m}$ is to 1, the stronger the continuum is. Since AGNs have weaker UIBs than starbursts, @Laurent2000 proposed to use the combination of the f$_{15\mu m}$/f$_{6.7\mu m}$ and f$_{6.7\mu m}$/f$_{6\mu m}$ colors to differentiate between the two mechanisms contributing to the MIR emission. Clearly there is a redshift dependence of this diagnostic due to the K-correction of the SEDs, but since the redshifts of our targets are small, these indicators can be applied [@Laurent1999a].

Using a large sample of galaxies in the Virgo cluster @Boselli1997 studied the properties of their MIR emission, normalized to the mass of these galaxies. This was done by examining the ratios of the f$_{6.7\mu m}$ (LW2) and f$_{15\mu m}$ (LW3) flux densities to the K band light, which scales with stellar mass of the galaxy, and it was found that the typical f$_{15\mu m}$/K ratio for a late type spiral ranges between 1 and 10. In Table \[k\_ha\], we present those ratios for our sample and we find that even though their active nuclei must contribute some non-thermal emission in the K band the ratios are considerably larger. This can be attributed to a 