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Nuclear Ring Formation in Barred Galaxies: a Requirement for Mass Inflow

Explore how nuclear rings impact mass inflow in barred galaxies, their formation theories, and the influence of bar characteristics on inflow rates through hydrodynamic modeling.

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Nuclear Ring Formation in Barred Galaxies: a Requirement for Mass Inflow

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  1. Nuclear Ring Formation in Barred Galaxies: a Requirement for Mass Inflow Michael W. Regan (STScI) & Peter J. Teuben (University of Maryland)

  2. Why study Nuclear Rings? • Can contain a significant fraction of star formation in the galaxy • Laboratory for star formation

  3. Why study Nuclear Rings? • Can contain a significant fraction of star formation in the galaxy • Laboratory for star formation • Cause large scale mass inflow • AGN fueling • Bar destruction/psuedobulge formation • Fueling of starburst rings

  4. Ring Formation Theories • Why do they form? • Trapped between the Inner Lindblad Resonances (ILRs) (Combes 1996; Buta & Combes 1996) • Circular orbits are stable (Shlosman, Begleman, & Frank 1990) • Remnant of nuclear starburst (Kenney, Carlstrom, & Young 1993) • Gas on X2 orbits interacts with gas on X1 orbits • Where do they form? • Peak of rotation curve • Peak of W-k/2 curve (Piner, Stone, & Teuben 1995) • At the Inner Inner Lindblad Resonance (IILR) when there are two or at the ILR if only one (Buta & Combes 1996)

  5. This presentation address how nuclear rings affect bar driven mass inflow. Where and why nuclear rings form Their effect on mass inflow Hydrodynamic modeling

  6. Hydrodynamic Modeling Example

  7. Bar Axis Ratio = 1.5 Bar Strength Central Mass Concentration

  8. Bar Axis Ratio = 2.0 Bar Strength Central Mass Concentration

  9. Bar Axis Ratio = 2.5 Bar Strength Central Mass Concentration

  10. Bar Axis Ratio = 3.0 Bar Strength Central Mass Concentration

  11. Bar Axis Ratio = 3.5 Bar Strength Central Mass Concentration

  12. Bar Orbits Why and where nuclear rings form

  13. X2 orbits are related to nuclear rings • Offset bar dust lanes and x2 orbit are strongly correlated (Athanassoula 1992) • Nuclear rings and offset bar dust lanes are strongly correlated • Expect to see x2 orbit and nuclear ring correlation.

  14. Bar Axis Ratio = 1.5 Bar Strength Central Mass Concentration

  15. Bar Axis Ratio = 2.0 Bar Strength Central Mass Concentration

  16. Bar Axis Ratio = 2.5 Bar Strength Central Mass Concentration

  17. Bar Axis Ratio = 3.0 Bar Strength Central Mass Concentration

  18. Bar Axis Ratio = 3.5 Bar Strength Central Mass Concentration

  19. Why do Nuclear Rings Form? • Gas cannot exist on both x1-like and x2-like streamlines in the same region • Gas appears to favor the x2-like streamlines • Consistent with van Albada & Sanders (1982) • Gas prefers more circular orbit • X2 orbits have lower energy

  20. How bar characteristics affect mass inflow

  21. Bar Axis Ratio = 3.0 Bar Strength Central Mass Concentration

  22. Bar Axis Ratio = 1.5 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  23. Bar Axis Ratio = 2.0 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  24. Bar Axis Ratio = 2.5 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  25. Bar Axis Ratio = 3.0 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  26. Bar Axis Ratio = 3.5 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  27. Bar Axis Ratio = 4.0 Inflow rate to 100pc radius Qb Bar Strength Inflow rate to inner Kpc Central Mass Concentration

  28. X1 rings form at the largest non-looping x1 orbit

  29. Bar Axis Ratio = 1.5 Bar Strength Central Mass Concentration

  30. Bar Axis Ratio = 2.0 Bar Strength Central Mass Concentration

  31. Bar Axis Ratio = 2.5 Bar Strength Central Mass Concentration

  32. Bar Axis Ratio = 3.0 Bar Strength Central Mass Concentration

  33. Bar Axis Ratio = 3.5 Bar Strength Central Mass Concentration

  34. Bar Axis Ratio = 4.0 Bar Strength Central Mass Concentration

  35. The Ring in NGC 6012 is an X1 ring I Band B-I

  36. Conclusions • Nuclear rings form at the radius of the largest x2 orbit

  37. Conclusions • Nuclear rings form at the radius of the largest x2 orbit • Only when nuclear rings form is there significant inflow.

  38. Conclusions • Nuclear rings form at the radius of the largest x2 orbit • Only when nuclear rings form is there significant inflow. • Weak bars have no effect on mass inflow

  39. Conclusions • Nuclear rings form at the radius of the largest x2 orbit • Only when nuclear rings form is there significant inflow. • Weak bars have no effect on mass inflow • Rings form due to intersecting orbits • Nuclear rings (x2 & x1 orbits) • X1/Inner Rings (self-looping x1 orbits)

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