  About 45% of the point sources detected in the 2 Ms Chandra exposure of the
HDF-N can be matched with moderately bright galaxies with z<1.4 that have been
studied by the Caltech Faint Galaxy Redshift Survey. Although the optical
spectra of these galaxies appear normal, based on their X-ray properties ~20%
of them appear to contain weak AGNs. More than 90% of the X-ray photons
detected by Chandra from galaxies within the redshift regime 0.4 < z < 1.1 are
powered by accretion onto massive black holes. For the sample of galaxies in
common, we use their emitted luminosity in the 3727 A line of [OII] to estimate
their star formation rate (SFR). The X-ray emitting galaxies are not those with
the highest rest frame equivalent width in this emission line, but rather are
among those with the highest SFR. With SFR corrected for inclination effects,
the distant galaxies show a L(X) -- SFR relationship that is comparable to that
of local galaxies. The HDF sample has a significantly higher median SFR and
median SFR/galaxy stellar mass than does a sample of local star forming
galaxies. We demonstrate that the observed SFR for most of the galaxies at z~1
in the HDF sample, if maintained as constant over their ages, suffices to
produce the stellar mass observed in these galaxies. A rise in SFR at still
earlier times is not required. We provide further evidence to support the
conclusion that, once AGNs are eliminated, X-ray emission in these distantstar
forming galaxies is related to the SFR through the same physical mechanisms
that prevail locally.
