  By detecting ionised-gas emission in 75% of the cases, the SAURON
integral-field spectroscopic survey has further demonstrated that early-type
galaxies often display nebular emission. Furthermore, the SAURON data have
shown that such emission comes with an intriguing variety of morphologies,
kinematic behaviours and line ratios.
  Perhaps most puzzling was the finding that round and slowly rotating objects
generally display uncorrelated stellar and gaseous angular momenta, consistent
with an external origin for the gas, whereas flatter and fast rotating galaxies
host preferentially co-rotating gas and stars, suggesting internal production
of gas. Alternatively, a bias against the internal production of ionised gas
and against the acquisition of retrograde material may be present in these two
kinds of objects, respectively.
  In light of the different content of hot gas in these systems, with slowly
rotating objects being the only systems capable of hosting massive X-ray halos,
we suggest that a varying importance of evaporation of warm gas in the hot
interstellar medium can contribute to explain the difference in the relative
behaviour of gas and stars in these two kinds of objects. Namely, whereas in
X-ray bright and slowly rotating galaxies stellar-loss material would quickly
evaporate in the hot medium, in X-ray faint and fast rotating objects such
material would be allowed to lose angular momentum and settle in a disk, which
could also obstruct the subsequent acquisition of retrograde gas. Evidence for
a connection between warm and hot gas phases, presumably driven by heat
conduction, is presented for four slowly rotating galaxies with CHANDRA
observations.
