Formation of gas disks in merging galaxies

Observations indicate that much of the interstellar gas in merging galaxies may settle into extended gaseous disks. Here, I present simulations of disk formation in mergers of gas-rich galaxies. Up to half of the total gas settles into embedded disks; the most massive instances result from encounters in which both galaxies are inclined to the orbital plane. These disks are often warped, many have rather complex kinematics, and roughly a quarter have counter-rotating or otherwise decoupled central components. Disks typically grow from the inside out; infall from tidal tails may continue disk formation over long periods of time.Comment: Submitted to MNRAS. 15 pages, 12 B&W figures, 1 color figure. See http://www.ifa.hawaii.edu/~barnes/fogdimg.html for versions with high-resolution figures, and http://www.ifa.hawaii.edu/~barnes/research/gassy_mergers/index.html for animations of the simulation

A simple algorithm for orbit classification

We describe a simple algorithm for classifying orbits into orbit families. This algorithm works by finding patterns in the sign changes of the principal coordinates. Orbits in the logarithmic potential are studied as an application; we classify orbits into boxlet families, and examine the influence of the core radius on the set of stable orbit families.Comment: 10 pages, 4 figures. Accepted for publication in MNRAS. For a version formatted for 8.5x11 paper, visit http://www.ifa.hawaii.edu/faculty/barnes/saoc.htm