  We use numerical simulations of structure formation in a Cold Dark Matter
model to predict the absorption lines in the soft X-rays produced by heavy
elements in the shock-heated intergalactic medium at low redshift. The
simulation incorporates a model for metal production in galaxies and the
subsequent dispersion of the metals to the intergalactic medium. We analyze in
particular absorption lines produced by oxygen, and calculate the ionization
stage taking into account the observed X-ray background at the present time. We
find that oxygen is fully ionized by the X-ray background in low-density voids,
and is mostly in the form of OVII and OVIII in the sheets and filamentary
regions. Strong absorption lines of OVII and OVIII with equivalent widths W ~
100 km/s are produced in filamentary regions of overdensities ~ 100 and
temperatures ~ 10^6 K, located in the outskirts of groups and clusters of
galaxies. The OVII line at E = 574 eV is generally the strongest one in these
systems. Our model predicts that any X-ray source (such as a quasar) should
typically show about one OVII absorption line with W > 100 km/s in the interval
from z=0 to z=0.3. These lines could be detected with the upcoming generation
of X-ray telescopes, and their origin in intervening systems could be confirmed
by the association with groups of galaxies and X-ray emitting halos near the
line-of-sight at the same redshift. The hot intergalactic medium may be one of
the main reservoirs of baryons in the present universe, and the heavy element
X-ray absorption lines offer a promising possibility of detecting this new
component in the near future.
