  Barred galaxies often develop a box/peanut pseudobulge, but they can also
host a nearly spherical classical bulge, which is known to gain rotation due to
the bar. We aim to explore how the presence of gas impacts the rotation of
classical bulges. We carried out a comprehensive set of hydrodynamical N-body
simulations with different combinations of bulge masses and gas fractions. In
these models, both massive bulges and high gas content tend to inhibit the
formation of strong bars. For low-mass bulges, the resulting bar is stronger in
cases of low gas content. In the stronger bar models, bulges acquire more
angular momentum and thus display considerable rotational velocity. Such bulges
also develop anisotropic velocity dispersions and become triaxial in shape. We
found that the rotation of the bulge becomes less pronounced as the gas
fraction is increased from 0 to 30%. These results indicate that the gas
content has a significant effect on the dynamics of the classical bulge,
because it influences bar strength. Particularly in the case of the low-mass
bulges (10% bulge mass fraction), all of the measured rotational and structural
properties of the classical bulge depend strongly and systematically on the gas
content of the galaxy.
