Download Counter-rotating Stellar Components in Simulated Disk Galaxies

2nd Regional Meeting of Extragalactic Astronomy
Córdoba, Argentina, November 30th - December 5th 1987.
Counter-rotating Stellar Components
in Simulated Disk Galaxies
Mario Abadi
Observatorio Astronómico de Córdoba & CONICET
and
David Algorry, Julio Navarro, Laura Sales, Matthias
Steinmetz, Franziska Piontek
Galaxies in the Dark Workshop
August 1st-4th 2011
Cafayate, Argentina
Outline
Observational Results
Cosmological Numerical Simulations
Analysis
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 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.
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
1) Mvir=1.50
2) Mvir=2.89
3) Mvir=4.05
4) Mvir=5.49
60 kpc
Virial
in 1011 M⊙
11 M
10masses
5) Mvir=6.61
6) Mvir=7.93
7) Mvir=13.79
Piontek & Steinmetz 2009
Line of Sight Velocity Distribution
d
2 kpc slit
d/kpc=-10,-6,-4,-2,+2,+4,+6,+10
Line of Sight Velocity
d=-10kpc
d=- 6kpc
d=- 4kpc
d=- 2kpc
d=+ 2kpc
d=+ 4kpc
d=+ 6kpc
d=+10kpc
Number
Circularity Distribution
C=Jz/Jcirc
C=-1
Counter-rotating star
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
C=+1
Co-rotating stars
Two well defined regions that help to
define two different structures:
Edge-On
Face-On
Co-rotating
Counter-rotating
Circularity
Co-rotating
Energy vs Circularity
Counter-rotating
Binding Energy
(Increasing Radius )
Co and Counter Rotating Stars
Y
Z
Y
X
Velocity Field
Co-rotating Disk
Y
Z
Y
X
Counter-rotating Bar
• (a,b,c)=(1.0,0.5,0.3)τ=0.74
Y
Z
Y
X
Mass Profile
Total
Halo
Stars
Gas
Star Formation Time Distribution
Old
Young
Star Formation Time Distribution
Bar
Disk
Stars in the bar are old
stars in the disk are
young
Old
Young
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
Angular Momentum Evolution
Jz
Jx
Disk =Gas + Stars
Barra=Gas + Stars
Jtot
Jy
Time/Gyr
Line of Sight Velocity Distribution
d
2 kpc slit
d/kpc=-10,-6,-4,-2,+2,+4,+6,+10
Line of Sight Velocity
d=+10kpc
d=+ 6kpc
d=+ 4kpc
d=+ 3kpc
d=+ 2kpc
d=- 2kpc
d=- 3kpc
d=- 4kpc
d=- 6kpc
d=-10kpc
Number
Circularity Distribution
C=Jz/Jcirc
C=-1
Counter-rotating star
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
C=+1
Co-rotating stars
Energy vs Circularity
Two well defined regions that help to
define two different structures:
Edge-On
Face-On
Circularity
Co-rotating
Counter-rotating
Binding Energy
(Increasing Radius )
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
Ring
Disk
Stars in the ring are
old stars in the disk
are young
Old
Young
Numerical Simulations
• Each halo simulated with 3 different Feedback
models: Standard, All in-Standard and All inLow 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
Ring Galaxy
Bared Galaxy
Standard
Circularity C=Jz/Jcirc
Circularity vs Feedback
All in-Standard
Ring Galaxy
Bared Galaxy
Standard
Circularity C=Jz/Jcirc
Circularity vs Feedback
All in-Standard
Ring Galaxy
Bared Galaxy
Standard
Circularity C=Jz/Jcirc
All in-Low Kinetic
Simulated Galaxies
1) Mvir=1.50
2) Mvir=2.89
3) Mvir=4.05
λ=0.040
λ=0.029
λ=0.034
λ=0.016
λ=0.026
λ=0.058
4) Mvir=5.49
λ=0.019
60 kpc
Virial
in 1011 M⊙
11 M
10masses
5) Mvir=6.61
6) Mvir=7.93
7) Mvir=13.79
Piontek & Steinmetz 2009
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, RixIC&4889
White 1992)