The imprint of dissipation on the shapes of merger remnant LOSVDs
  The properties of elliptical galaxies are broadly consistent with simulated
remnants of gas-rich mergers between spirals, motivating more detailed studies
of the imprint of this formation mechanism on the remnant distribution
function. Gas has a strong impact on the non-Gaussian shapes of the
line-of-sight velocity distributions (LOSVDs) of the merger remnant, owing to
the embedded disk that forms out of the gas that retains its angular momentum
during the merger, and the strong central mass concentration from the gas that
falls to the center. The deviations from Gaussianity are parametrized by the
Gauss-Hermite moments h_3 and h_4, which are related to the skewness and
kurtosis of the LOSVDs. We quantify the dependence of the (h_3,h_4)-v/sigma
relations on the initial gas fraction of the progenitor disks in 1:1 mergers,
using Gadget-2 simulations including star formation, radiative cooling, and
feedback from supernovae and AGN. For gas fractions f_gas < ~15% the overall
correlation between h_3 and v/sigma is weak, consisting of a flat negatively
correlated component arising from edge-on viewing angles plus a steep
positively correlated part from face-on projections. The spread in v/sigma
values decreases toward high positive h_4, and there is a trend toward lower
h_4 as the gas fraction increases from 0 to 15%. For f_gas > ~20% the (h_3,4)-
v/sigma distributions look quite different - there is a tight negative h_3-
v/sigma correlation, and a wide spread in v/sigma values at all h_4, in better
agreement with observations. Re-mergers of the high-f_gas remnants (dry
mergers) produce slowly rotating systems with nearly Gaussian LOSVDs. We
explain all of these trends in terms of the underlying orbit structure of the
remnants, as molded by their dissipative formation histories.
