Overlay of 3C15 X-ray contours (in 0.3-7.0 keV) on
HST optical image after subtraction of galaxy.

Note the inner X-ray knot has no obvious optical
association, while the outer X-ray knot aligns well
with the outermost optical feature. This suggests huge
differences in the populations of electrons responsible
for these two bands of emission, or that very different
emission processes are operating.