Nuclear Rings
- Form by resonant interactions with barred potentials + but bar torque is low near inner lindbland resonances + resonance is very long timescale
- claim that bar strength controls bar substructure
- bar potential modeled by "Ferrers Prolates"
- Q_B is the "controlling parameter" + Q_B = 0.23 yields really cool looking models
- stronger bar leads to smaller radius ring + pushes more gas inward
- range of SFR + age gradient within nuclear rings
Two models of ring SF
- popcorn model + randomly distributed + no age gradient
- pearls-on-a-string model + SF at contact point + age gradient
- age gradient <-> lower SFR
- simulation generating 10^5 msun clusters
Sim results
- presence or absence of age gradient depends on SFR + no age gradient if SFR > 1 Myr + corresponds to maximum SFR at a contact point
- prolonged SF requires prolonged feeding + HVCs (accretion of primordial gas) + ang mom dissipation by spiral arms + Galactic fountains
- If corotation radius at large R, can feed spiral arms into ring
Questions
- Q: Sims are pure hydro. Speculate on B-fields. Chuckle.
- A: Ring would be smaller
- Q: Typical velocity of gas along bar in model?
- A: 50-100 km/s
- Q: Do you mean no need for x2 orbit?
- A: no, need X2 to form ring. Formation mechanism of ring is not related to resonance.
- Q: Ring on x2 orbit?
- A: yes
- Q: is there observation evidence of age gradients in nuclear rings?
- A: Yes, Mazzuca '08 shows gradient in H-alpha EQW
- Q Farhad: Can you form the circumnuclear disk (2pc) with the same mechanism?
- A: Can't answer now. Need to run the simulation with the right size-scale
- Q: Would the bar be unstable to bending instabilities in 3D?
- A: We ran 3D, and didn't see any difference. But, with different initial conditions, may see dynamical difference..
- Q: Have you modeled where the bar meets the arm?
- A: No, couldn't do that, only treated stellar.