Computer Science – Performance
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...20517701y&link_type=abstract
American Astronomical Society Meeting 205, #177.01; Bulletin of the American Astronomical Society, Vol. 37, p.380
Computer Science
Performance
Scientific paper
We introduce a new set of high-performance CFD codes we have developed for astrophysical disks, the Antares Codes. They are second-order Godunov codes featured with the exact Riemann solver, and the fft Poisson solver for self-gravitation. Characteristic decompositions are performed on the boundary, to guarantee the true radiation (non-reflecting) boundary conditions. In this report, we use the Antares codes to study the redistribution of the mass in a gas-dust disk under the influence of a rotating bar potential, in order to understand the fuelling mechanism of AGNs and starburst ring activities and the formation of dense circumnuclear molecular disks. Spiral density waves are excited at three resonances in the disk, namely, the outer Lindblad resonance (OLR), the outer inner Lindblad resonance (OILR), and the inner inner Lindblad resonances (IILR). Associated with these waves are the angular momentum transports between the disk and the bar, and gas in the disk will redistribute accordingly. Gas accumulated near the OLR forms the spiral-ring structure, which often becomes unstable and develops into chaos. The instability occurs when Toomre's criterion is violated, i.e., Q<1, and it can be identified to be the starburst rings. The gas disk at the OILR near the center, however, remains stable even with extremely high surface density. It can be understood that the high values of epicyclic frequency or angular speed there provide sufficient inertia force to keep the nuclear gas disk from collapsing. This explains the origin of the dense circumnuclear molecular disks, which would be a reservoir to supply the fuel for AGN's. The work is supported in parts by a Key Project of Academia Sinica and National Science Council grant 91-2112-M-011-070.
Yen David C. C.
Yuan Changhe
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