  Using the 1 Ms Chandra Deep Field North and 15 micron ISOCAM HDF-N surveys we
find a tight correlation between the population of strongly evolving starbursts
discovered in faint 15 micron ISOCAM surveys and the apparently normal galaxy
population detected in deep X-ray surveys. Up to 100% of the X-ray detected
emission-line galaxies (ELGs) have 15 micron counterparts, in contrast to
10-20% of the X-ray detected absorption-line galaxies and AGN-dominated
sources. None of the X-ray detected ELGs is detected in the hard band (2-8
keV), and their stacked-average X-ray spectral slope of Gamma=2.0 suggests a
low fraction of obscured AGN activity within the X-ray detected ELG population.
The characteristics of the z=0.4-1.3 X-ray detected ELGs are consistent with
those expected for M82 and NGC 3256-type starbursts; these X-ray detected ELGs
contribute ~2% of the 0.5-8.0 keV X-ray background. The only statistical
difference between the X-ray detected and X-ray undetected 15 micron selected
ELGs is that a much larger fraction of the former have radio emission.
