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Bar-driven Evolution and Instability of Self-gravitating Disks

Bar-driven Evolution and Instability of Self-gravitating Disks. Chi Yuan Institute of Astronomy and Astrophysics Academia Sinica, Taipei, Taiwan, ROC David C.C. Yen, Yi-Hsin Liu, Chao-Chin Yang. Three Observational Facts. Starburst rings Dense circumnuclear molecular disks

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Bar-driven Evolution and Instability of Self-gravitating Disks

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  1. Bar-driven Evolution and Instability of Self-gravitating Disks Chi Yuan Institute of Astronomy and Astrophysics Academia Sinica, Taipei, Taiwan, ROC David C.C. Yen, Yi-Hsin Liu, Chao-Chin Yang

  2. Three Observational Facts • Starburst rings • Dense circumnuclear molecular disks • Gas depression central regions

  3. Starburst Rings NGC4313 NGC1512 NGC6782

  4. Circumnuclear Disk in ngc1068

  5. Center of M51

  6. The 3-kpc Arm

  7. Gas Distribution in the Milky Way

  8. CO and HCN in theMilky Way

  9. Distribution of Gas inGalactic Disks

  10. Diamond-shaped Ring in NGC6782

  11. NGC 1068 • Type : Sb / AGN • Distance : 14.4 Mpc ( H0 =75 km s-1 Mpc-1 ) 1 arcsec = 74 pc 9.5 arcmin

  12. The Antares Code 大火程序 • A high-performance CFD-MHD code for astrophysics • It is a second-order Godunov code (or codes) equipped with exact Riemann solver and the balance law correction. (2-D) • It is also featured with the fft Poisson solver, to include the self-gravitation of the disk, and with characteristics decomposition on the boundary, to guarantee the true radiation (non-reflecting) boundary conditions.

  13. Governing Equations

  14. Schematic Picture of a Bar In Numerical Simulations

  15. Nearly Flat Rotation Curve OILR OLR

  16. Cases of Double Resonances: OLR-OILR

  17. Double Ring Feature

  18. Elmegreen Rotation Curve

  19. Cases for a Single OLR

  20. Evolution of Self-gravitating Disks

  21. Double Rings and Central Spirals

  22. Double Rings and Central Spirals

  23. Q-value for Self-gravitating Disk

  24. Onset of Instability

  25. Disk Instability

  26. Conclusions • Starburst rings are the results of a gaseous disk responding to a rotating bar potential. But, there are many possibilities. • A fast nuclear bar like NGC1068 or the Milky Way (OLR and OILR) • A fast nuclear bar like possibly NGC4313 (OLR).

  27. Conclusions cont. • A double ring due slow bar • like NGC6278 (OLR-OILR). • A fast bar in the center solves the starburst ring, dense circumnuclear molecular disk, and depletion of gas in between all together. • Self-gravitation plays an important role. It leads to instability, chaos, and star formation • Toomre’s criterion Q=1 works extremely well.

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