2 nd Regional Meeting of Extragalactic Astronomy

1. 2nd Regional Meeting of Extragalactic Astronomy Córdoba, Argentina, November 30th - December 5th 1987.

2. Counter-rotating Stellar Components in Simulated Disk Galaxies Mario Abadi ObservatorioAstronómico de Córdoba & CONICET and David Algorry, Julio Navarro, Laura Sales, Matthias Steinmetz, FranziskaPiontek Galaxies in the Dark Workshop August 1st-4th 2011 Cafayate, Argentina

3. Outline Observational Results Cosmological Numerical Simulations Analysis Preliminary Conclusions

4. Counter-rotating Car

5. Observational Results There is observational evidence of counter-rotation in early type spiral galaxies • NGC 4550 an E7/S0 galaxy (Rix et al 1992) 2) Counter-rotating stars in the disk of the SAB galaxy NGC 7217 (Merrifield & Kuijken 1994) 3) Counter-rotating Stellar Disks in Early-Type (Sa) Spirals: NGC 3593 (Bertola et al 1996) NGC 3593 NGC 7217

6. NGC 4550 • Line of sight velocity distribution along the major axis shows striking bimodality. This bimodality indicates the presence of two disk components, photometrically inseparable, but counterstreaming at projected velocities of -100km/s and +150km/s (Rix et al 1992)

7. NGC 5728 Line of Sight Velocity • NGC 5728 is an spiral barred Sb galaxy with a counter-rotating central component (Prada & Gutierrez 1999) • Dynamical instabilities, retrograde accretion of gas (or satellites) are proposed to explain this component.

8. NGC 7331 Prada et al (1996) found that the line-of-sight velocity distribution has two distinct peaks and can be decomposed into a fast-rotating component with v/σ ~ 3, and a slower rotating, retrograde component with v/σ ~1–1.5. The radial surface brightness profile of the counter-rotating component follows that of the bulge, while the fast-rotating component follows the disk.

9. Numerical Simulations • Zoom-in Cosmological Numerical Simulations in the λCDM model (Piontek & Steinmetz 2009) • Gravitation, Hydrodynamics, Cooling, Star Formation, Feedback • Temporal evolution from redshiftz=50 to z=0 • 7 different galactic halos • 1.5<Mvir/(1011 M⊙)<13.8 • Gas: mpar=4.9×105 M⊙ and ε=1.0 kpc • Dark: mpar=2.3×106 M⊙ and ε=1.4 kpc

10. Simulated Galaxies 3) Mvir=4.05 4) Mvir=5.49 1) Mvir=1.50 2) Mvir=2.89 1011 M 60 kpc Virial masses in 1011 M⊙ 5) Mvir=6.61 6) Mvir=7.93 7) Mvir=13.79 Piontek & Steinmetz 2009

11. Line of Sight Velocity Distribution d 2 kpc slit d/kpc=-10,-6,-4,-2,+2,+4,+6,+10

12. Line of Sight Velocity d=-10kpc d=- 6kpc d=- 4kpc d=- 2kpc d=+ 2kpc d=+ 4kpc d=+ 6kpc d=+10kpc

13. Circularity Distribution Circularity: ratio between the z-component of the angular momentum Jz and the angular momentum of the circular orbit with the same binding energy Jcirc(E) This distribution for all star particles inside a sphere of radius 30 kpc has 2 peaks: one at c=+1.0 and the other one at c=-0.5 Number C=Jz/Jcirc C=-1 C=+1 Counter-rotating star Co-rotating stars

14. Energy vs Circularity Two well defined regions that help to define two different structures: Edge-On Face-On Co-rotating Counter-rotating Circularity Co-rotating Counter-rotating Binding Energy (Increasing Radius )

15. Co and Counter Rotating Stars Y Z Y X

16. Velocity Field

17. Co-rotating Disk Y Z Y X

18. Counter-rotating Bar • (a,b,c)=(1.0,0.5,0.3)τ=0.74 Y Z Y X

19. Mass Profile Total Halo Stars Gas

20. Star Formation Time Distribution Old Young

21. Star Formation Time Distribution Bar Disk Stars in the bar are old stars in the disk are young Old Young

22. Star Formation Time Distribution Bar Disk z=0 z=0 Stars in the bar are old stars in the disk are young Old Young z=0 z=0

23. Angular Momentum Evolution Disk =Gas + Stars Jz Jx Barra=Gas + Stars Jtot Jy Time/Gyr

24. Line of Sight Velocity Distribution d 2 kpc slit d/kpc=-10,-6,-4,-2,+2,+4,+6,+10

25. Line of Sight Velocity d=+10kpc d=+ 6kpc d=+ 4kpc d=+ 3kpc d=+ 2kpc d=- 2kpc d=- 3kpc d=- 4kpc d=- 6kpc d=-10kpc

26. Circularity Distribution Circularity: ratio between the z-component of the angular momentum Jz and the angular momentum of the circular orbit with the same binding energy Jcirc(E) This distribution for all star particles inside a sphere of radius 30 kpc has 2 peaks: one at c=+1.0 and the other one at c=-0.8 Number C=Jz/Jcirc C=-1 C=+1 Counter-rotating star Co-rotating stars

27. Energy vs Circularity Two well defined regions that help to define two different structures: Edge-On Face-On Co-rotating Circularity Counter-rotating Binding Energy (Increasing Radius )

28. Co and Counter Rotating Stars

29. Co-rotating Disk

30. Counter-rotating Ring • (a,b,c)=(1.0,1.0,0.3) τ=0.04

31. Star Formation Time Distribution Old Young

32. Star Formation Time Distribution Ring Disk Stars in the ringare old stars in the disk are young Old Young

33. Numerical Simulations • Each halo simulated with 3 different Feedback models: Standard, All in-Standard and All in-Low Kinetic • All in=standard feedback model in combination with additional physical processes like a UV background, kinetic feedback, a delayed energy deposition as expected for type Ia supernovae, mass return

34. Circularity vs Feedback Standard Bared Galaxy Ring Galaxy Circularity C=Jz/Jcirc

35. Circularity vs Feedback Standard All in-Standard Bared Galaxy Ring Galaxy Circularity C=Jz/Jcirc

36. Circularity vs Feedback All in-Low Kinetic Standard All in-Standard Bared Galaxy Ring Galaxy Circularity C=Jz/Jcirc

37. Simulated Galaxies 3) Mvir=4.05 4) Mvir=5.49 1) Mvir=1.50 2) Mvir=2.89 λ=0.040 λ=0.029 λ=0.034 λ=0.019 λ=0.016 λ=0.026 λ=0.058 1011 M 60 kpc Virial masses in 1011 M⊙ 5) Mvir=6.61 6) Mvir=7.93 7) Mvir=13.79 Piontek & Steinmetz 2009

38. Preliminary Conclusions • Simulated galaxies show counter-rotating stellar components • Stars in the counter-rotating components seems to be old and could have bar/ring shape • Seems to be related to low spin halos

39. Observational Results • In the last 2 decades, or so, there has been increasing evidence of kinematic peculiarities in elliptical galaxies that may be explained by a counter-rotating nuclear disk. (e.g. Franx & Illingworth 1988, Bender et al 1994, Rix & White 1992) IC 4889