Discovery of Counter-Rotating Gas in the Galaxies NGC1596 and NGC3203 and the Incidence of Gas Counter-Rotation in S0 Galaxies

We have identified two new galaxies with gas counter-rotation (NGC1596 and NGC3203) and have confirmed similar behaviour in another one (NGC128), this using results from separate studies of the ionized-gas and stellar kinematics of a well-defined sample of 30 edge-on disc galaxies. Gas counter-rotators thus represent 10+/-5% of our sample, but the fraction climbs to 21+/-11% when only lenticular (S0) galaxies are considered and to 27+/-13% for S0s with detected ionized-gas only. Those fractions are consistent with but slightly higher than previous studies. A compilation from well-defined studies of S0s in the literature yields fractions of 15+/-4% and 23+/-5%, respectively. Although mainly based on circumstantial evidence, we argue that the counter-rotating gas originates primarily from minor mergers and tidally-induced transfer of material from nearby objects. Assuming isotropic accretion, twice those fractions of objects must have undergone similar processes, underlining the importance of (minor) accretion for galaxy evolution. Applications of gas counter-rotators to barred galaxy dynamics are also discussed.Comment: 8 pages, including 1 table and 2 figures. Accepted for publication in MNRAS. Version with full resolution figures available at http://www-astro.physics.ox.ac.uk/~bureau/pub_list.htm

A unified approach to compute foliations, inertial manifolds, and tracking initial conditions

Several algorithms are presented for the accurate computation of the leaves in the foliation of an ODE near a hyperbolic fixed point. They are variations of a contraction mapping method in [25] to compute inertial manifolds, which represents a particular leaf in the unstable foliation. Such a mapping is combined with one for the leaf in the stable foliation to compute the tracking initial condition for a given solution. The algorithms are demonstrated on the Kuramoto-Sivashinsky equation

Chemical reaction in a turbulent flow field with uniform velocity gradient

Chemical reactions in turbulent flow fields with uniform velocity gradien