2nd Regional Meeting of Extragalactic AstronomyCórdoba, Argentina, November 30th - December 5th 1987.
Counter-rotating Stellar Components in Simulated Disk Galaxies
Mario Abadi Observatorio Astronómico de Córdoba & CONICET
andDavid Algorry, Julio Navarro, Laura Sales, Matthias
Steinmetz, Franziska Piontek
Galaxies in the Dark WorkshopAugust 1st-4th 2011Cafayate, Argentina
OutlineObservational ResultsCosmological Numerical SimulationsAnalysis Preliminary Conclusions
Counter-rotating Car
Observational Results
There is observational evidence of counter-rotation in early type spiral galaxies
1) 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 7217 NGC 3593
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)
NGC 5728
• 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.
Line of Sight Velocity
NGC 7331Prada 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.
Numerical Simulations
• Zoom-in Cosmological Numerical Simulations in the λCDM model (Piontek & Steinmetz 2009)
• Gravitation, Hydrodynamics, Cooling, Star Formation, Feedback
• Temporal evolution from redshift z=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
Simulated Galaxies
1011 M
60 kpc
1) Mvir=1.50 2) Mvir=2.89 3) Mvir=4.05 4) Mvir=5.49
5) Mvir=6.61 6) Mvir=7.93 7) Mvir=13.79 Piontek & Steinmetz 2009
Virial masses in 1011 M⊙
Line of Sight Velocity Distribution
2 kpc slit
d/kpc=-10,-6,-4,-2,+2,+4,+6,+10
d
Line of Sight Velocity
d=-10kpcd=- 6kpcd=- 4kpcd=- 2kpcd=+ 2kpcd=+ 4kpcd=+ 6kpcd=+10kpc
Circularity Distribution
Num
ber
C=Jz/Jcirc
C=-1 C=+1Counter-rotating star Co-rotating stars
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
Energy vs Circularity
Binding Energy(Increasing Radius )
Coun
ter-
rota
ting
Ci
rcul
arity
C
o-ro
tatin
g
Two well defined regions that help to define two different structures:
Co-rotating
Counter-rotating
Edge-On Face-On
Co and Counter Rotating Stars
X
YZ
Y
Velocity Field
Co-rotating Disk
X
YZ
Y
Counter-rotating Bar • (a,b,c)=(1.0,0.5,0.3)τ=0.74
X
YZ
Y
Mass Profile
Gas
Stars
Halo
Total
Star Formation Time Distribution
Old Young
Star Formation Time Distribution
Old Young
DiskBar
Stars in the bar are old stars in the disk are young
Star Formation Time Distribution
Old Young
DiskBar
Stars in the bar are old stars in the disk are young
z=0z=0
z=0z=0
Angular Momentum EvolutionDisk =Gas + Stars
Barra=Gas + Stars
Jx
Jy
Jz
Jtot
Time/Gyr
Line of Sight Velocity Distribution
2 kpc slit
d/kpc=-10,-6,-4,-2,+2,+4,+6,+10
d
Line of Sight Velocity
d=+10kpcd=+ 6kpcd=+ 4kpcd=+ 3kpcd=+ 2kpcd=- 2kpcd=- 3kpcd=- 4kpcd=- 6kpcd=-10kpc
Circularity Distribution
Num
ber
C=Jz/Jcirc
C=-1 C=+1Counter-rotating star Co-rotating stars
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
Energy vs Circularity
Binding Energy(Increasing Radius )
Circ
ular
ity
Two well defined regions that help to define two different structures:
Co-rotating
Counter-rotating
Edge-On Face-On
Co and Counter Rotating Stars
Co-rotating Disk
Counter-rotating Ring• (a,b,c)=(1.0,1.0,0.3) τ=0.04
Star Formation Time Distribution
Old Young
Star Formation Time Distribution
Old Young
Ring Disk
Stars in the ring are old stars in the disk are young
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
Circularity vs Feedback
Circularity C=Jz/Jcirc
Ring
Gal
axy
Bare
d G
alax
y
Standard
Circularity vs Feedback
Circularity C=Jz/Jcirc
Ring
Gal
axy
Bare
d G
alax
y
Standard All in-Standard
Circularity vs Feedback
Circularity C=Jz/Jcirc
Ring
Gal
axy
Bare
d G
alax
y
Standard All in-Low KineticAll in-Standard
Simulated Galaxies
1011 M
60 kpc
1) Mvir=1.50 2) Mvir=2.89 3) Mvir=4.05 4) Mvir=5.49
5) Mvir=6.61 6) Mvir=7.93 7) Mvir=13.79
λ=0.040 λ=0.029 λ=0.019
λ=0.016 λ=0.026 λ=0.058
λ=0.034
Piontek & Steinmetz 2009
Virial masses in 1011 M⊙
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
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