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The Corotation Resonance and the Morphology of Galaxies

The Corotation Resonance and the Morphology of Galaxies. Xiaolei Zhang Naval Research Laboratory Ron Buta University of Alabama. What is the corotation resonance (CR)?.

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The Corotation Resonance and the Morphology of Galaxies

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  1. The Corotation Resonance and the Morphology of Galaxies Xiaolei Zhang Naval Research Laboratory Ron Buta University of Alabama

  2. What is the corotation resonance (CR)? If a galaxy has a coherent, quasi-steady spiral, bar, or oval pattern rotating at a pattern speed Ωp, corotation occurs where the circular angular velocity, Ω, equals Ωp. <--------- pattern speed Rotation curve Angular frequency curve

  3. Why is corotation important? divides disk into regions where wave interacts differently with stars - inside CR, stars lose angular momentum to wave - outside CR, the opposite occurs - net effect: angular momentum is transferred outwards -if CR is known, pattern speed may be derived, and locations of other resonances inferred

  4. How do you locate corotation? In general, however, locating CR requires other information besides morphology In some galaxies you can almost “eyeball” the likely location of CR! Multi-ringed galaxy NGC 3081

  5. The Tremaine-Weinberg 1984method* continuity equation -constant M/L -mainly SB0 galaxies NGC 936: Merrifield & Kuijken 1995,MNRAS 274, 933 *ApJ, 282, L5

  6. Canzian (1993) residual velocity field method* Residual velocity field shows change from 1 to 3 arms at CR Velocity field of disk with spiral density wave *ApJ, 414, 487

  7. The Phase Shift Method to Locate Corotation(s) Zhang (1996, ApJ, 457, 125): density wave patterns induce collective instabilities secular energy and angular momentum exchange process between disk matter and wave pattern -mediated by local gravitational instability, or collisionless shock

  8. Integral manifestation of this process is an azimuthal phase shift between potential and density spirals. Corotation (CR) occurs at major positive/negative phase shift crossings

  9. Phase shift leads to secular torquing action between wave and underlying disk stars Matter inside CR drifts inward, matter outside drifts outward Mechanism can lead to secular bulge growth

  10. Physical Basis of the Phase Shift Method

  11. Definition of the Phase Shift Zhang (1996)

  12. Radial mass accretion/excretion rates due to the phase shift

  13. Application of the Phase Shift Method using Near-Infrared Images Image Sources Eskridge et al., 2002, ApJS, 143, 73 Laurikainen et al. 2004, MNRAS, 355, 1251 Laurikainen, Salo, & Buta, MNRAS, 362, 1319 Block et al. 2004, AJ, 128, 283 Kennicutt et al. 2003, PASP, 115, 928

  14. The SBa galaxy NGC 4314 Two positive/negative crossings ----> two corotations

  15. The SB0/a Galaxy NGC 4596 Two corotations (circles) Hatched area: error bounds of TW method (Gerssen et al. 1999)

  16. NGC 1530 - radial mass accretion/excretione V-Ks color index map 2.2 micron Ks-band Surface mass density map corrected for stellar M/L effects (Bell & de Jong 2001) V-Ks map corrected for bar dust lanes B, C, D deprojected

  17. Results for NGC 1530 Phase shift plot versus radius Mass accretion/excretion rate versus radius Two corotations

  18. Results for M100 Most recent TW method study: Hernandez et al. 2005, ApJ, 632, 253 3 corotations: bar CR (blue); spiral CR(yellow) + central (not shown) Phase shift method: 3 corotations (red circles) 3.6 micron SINGS Legacy (Spitzer) image

  19. Analysis of the OSUBGS Sample(Eskridge et al. 2002)

  20. NGC 4548 NGC 7552

  21. NGC 2559 NGC 3059

  22. NGC 4314 NGC 5850

  23. NGC 5921 NGC 7479

  24. NGC 3513 Green circle - negative/positive crossing NGC 6221

  25. NGC 4665 NGC 150

  26. NGC 3338 NGC 4051

  27. NGC 5054 NGC 5247

  28. NGC 5248 NGC 7083

  29. NGC 613 NGC 3261

  30. Conclusions the PS method is promising new way of locating corotation(s) in disk galaxies Many bars appear to extend to CR, as predicted theoretically Application to full disk galaxy sequence is possible further evaluations and comparisons with other methods needed and planned results will lead to new insights on galaxy evolution

  31. Acknowledgments Ron thanks Eija Laurikainen, Heikki Salo, Johan Knapen, and the SINGS team for images used for this analysis. Funding for the OSUBGS was provided by grants from the NSF with additional funding from the Ohio State University.

  32. Speaking of galaxy morphology… The de Vaucouleurs Atlas of Galaxies By Ronald J. Buta, Harold G. Corwin, Jr.,and Stephen C. Odewahn Set for publication by Cambridge University Press in late 2006

  33. The De Vaucouleurs (1959) Revised Hubble Classification System

  34. Cross Section at Stage Sb

  35. NGC 4340 NGC 4596 NGC 4754 NGC 4608 IC 4290 NGC 1433 NGC 5850 NGC 5921 NGC 1073 NGC 4519 NGC 4027 NGC 4618 The de Vaucouleurs Atlas of Galaxies (Buta, Corwin, & Odewahn 2006): B-band images

  36. Barred spiral varieties (B-band) NGC 2523 SB(r) NGC 266 SB(rs) NGC 1300 SB(s) NGC 1433 SB(r) NGC 4548 SB(rs) NGC 7479 SB(s)

  37. Intrinsic SB Inner Ring Shapes (b/a)=0.6-1.0 IC 5240 NGC 7098 NGC 6782 NGC 1433

  38. Multi-armed ringed, barred spirals NGC 3124 NGC 2336 NGC 3953 NGC 7723

  39. Outer-ringed barred galaxies NGC 1326 NGC 1543 NGC 1291 NGC 2217 NGC 2859 NGC 3945

  40. Bar strength as a continuous property NGC 3992 SB NGC 210 SAB IC 1993 SA

  41. The End

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