Balancing the Baryon Budget: The fraction of the IGM due to Galaxy
  Mergers
  Observations indicate that roughly 60% of the baryons may exist in a Warm-Hot
Intergalactic Medium (WHIM) at low redshifts. Following up on previous results
showing that gas is released through galaxy mergers, we use a semi-analytic
technique to estimate the fraction of gas mass lost from haloes solely due to
mergers. We find that up to ~25% of the gas in a halo can unbind over the
course of galaxy assembly. This process does not act preferentially on smaller
mass haloes; bigger haloes \emph{always} release larger amounts of gas in a
given volume of the Universe. However, if we include multi-phase gas accretion
onto haloes, we find that only a few percent is unbound. We conclude that
either non-gravitational processes may be in play to heat up the gas in the
galaxies prior to unbinding by mergers or most of the baryons in the WHIM have
never fallen into virialised dark matter haloes. We present a budget for
stocking the WHIM compiled from recent work.
