1. Ensenada 08
The Formation of Disk Galaxies.
Improvements, Challenges, Artificial Images
F.Governato,AlysonBrooks,G.Stinson(MacMaster)
B.Willman(CfA), L.Mayer (Zurich), T.Quinn, C.Brook, L. MacArthur
(Caltech), J.Wadsley (McMaster) & the UW N-Body Shop
+ Patrik Jonsson (UCSC)

2. • Physical and Numerical Processes affecting
the Mass Distribution in L* Galaxies
•Artificial Images: Comparing Simulations with
Observations
•The Assembly of Galaxy Disks: Shocks or Cold Flows?

3. Cosmological hydro simulations of MW formation.
(Ngas, Ndm > 106 within Rvir + BlastWave feedback model )
(Governato, Willman, Mayer et al. 2006, 2007)
Frame = 200 kpc
Green= Gas
Blue & Red = Stars
zLMM: z = 1.
Spin = 0.036
Rd (I band) = 7.3 kpc
B/D (I band) = 0.37
U-R = 1.55
WMAP cosmology
Run carried to z=0
~ 100k CPU hrs.

4. cosmological galaxy formation: 10 Galaxies
Volume renormalization technique:
~ 100 - 300 pc spatial resolution in a
50Mpc box (DM + GAS)
300 Mpc
Large scale tidal torques preserved,
crucial for angular momentum of halos
Halos masses: 1010- 3 x 1012 Mo
Range of Last major merger: ~ 5 - 1
Range of halo spins: 0.01 - 0.05
Within Virial Radius: 1e6 DM,
3 Mpc
1e6 Gas ,
2-3e6 star particles.

5. Star Formation/Feedback
Gas Stars
Dynamical time Kroupa IMF
SF efficiency Padova lifetimes
SF
Threshold
Winds
Metals < 8 Msun
Blast SN Ia
Wave > 8 Msun
No
Cooling SN II
Stinson et al 2006
2 free parameters: C*, eSN

6. So What Does
Feedback Do?

7. MW Satellites:
UV field + SN feedback on
B
A
R Cosmic Abundance
Y
O
N
S
T
O
D 30-50 Km/sec
M
R
A
T
I
O

8. But Feedback crucial to regulate star formation
Effect of blastwave feedback on SFH of galaxy with halo of 1011 Mo
If blastwave feedback is
on, star formation peaks at
Last Major Merger
z< 1
AFTER
Feedback OFF
Last Major Merger.
Feedback ON
Progenitors forms
stars inefficiently due
to feedback
SF in bulges suppressed.
SFH includes all progenitors at any given time

9. SN Feedback: important at M< L*

10. How have Simulations
of Galaxy Formation improved
over the past few years?
Algorithms + CPU Power (N: 10k to 3-5 million)
Description of Physical Processes

11. I - Physical and Numerical Processes
affecting the DM&baryon distribution
In the central regions of Galaxies
Catinella et al 06 Governato et al 07
100.000 DM
Vrot
1.000.000 DM
Vrot converges
at 2-3 Rd
R/Rd R kpc

12. GADGET-2, No Feedback Naab et al Apj 07
Peak Vel
decreases 30%
as mass
resolution
Increases
125 fold.

13. Effects of Feedback. Zavala et al 08
No FB FB on.

14. L. Mayer, 08
The effects of limited resolution in gaseous disks
Embedded in a DM + hot gas halo.
Isolated disk galaxy + hot halo
N=1.000.000 100.000 30.000
Eps 0.5kpc 0.5kpc 2kpc

15. Mass Distribution of Galaxies
Resolution & Feedback Effects
in a Milky Way sized galaxy
No Star Formation
Star Formation
Star Formation+SN
Feedback does not
Change the mass
distribution unless
Coupling ~ 100%

16. Mass Distribution of Galaxies
Resolution & Feedback Effects
in a Milky Way sized galaxy
Resolution
+
Star Formation
+
SN.

17. Baryon Distribution
Gas Fraction
Small Galaxies: Feedback
L* : Star Form. +Feedback +Resolution
Galaxies>L* : SF+ Resolution
Vc

18. Angular Momentum Loss in Galaxies
• Dynamical friction on cold gas Navarro & White 96
• Angular Mom. Transfer in Gas Spiral waves:
Linden-Bell & Kalnajs 1971
• Torques from “grainy” DM halos (T.Kaufmann 07)
• Artificial Viscosity @Hot/Cold gas Interface
(Okamoto 06)

19. Size of Disks: Cold gas

20. Rotation Curves Revisited
High-res galaxies - > 106 dm and gas/stars particles within Rvir
Galaxies contain the right
AmountKm/sec
320
of baryon and DM
Within a few Rds
205 Km/sec
118 Km/sec

21. Using Sunrise…
Monte-Carlo method
“Photons” are emitted and scattered/absorbed stochastically
(courtesy Patrik Jonsson)
http://www.ucolick.org/~patrik/sunrise/
Stars
Gas & Metals
Dust follows the metal distribution of the gas component
See also codes by Narayanan and Chakrabarti

22. A Multi Color, Dust reddened Milky Way like Galaxy
formed in a cosmological simulation.

23. (Blastwave) Feedback makes larger disks

24. ..and so does resolution
MW-sized galaxy (halo has ~1012 Mo, ~ 0.05)
N=DM+Gas+stars Images with SUNRISE
Rd=30% smaller

25. Theory vs Observations
Kinematic vs Photometric
Decompositions

26. The L* Sample.
I Band Rds:
3 - 9kpc
I band
Bulge/Disk
ratios
0.3 - 0.5
High Resolution
L* Sample
(reddened)

27. Outline:

28. The Velocity- Size Relation
Courteau 07
Sa
High
Res
V: W20
Mag: Sunrise

29. The Assembly of Galaxy
Components: The Disk
Baugh et al 06

30. The New Model of Gas accretion: Cold Flows
“Cold mode”
(Keres et al. 04) hot accretion
of galactic gas
accretion:
gas creeps along
the equilibrium
line between
heating and
Cooling. It never
Shocks to Tvir.
cold accretion
Courtesy of Hoeft & Yepes

31. Gas Accretion I: disk stars @ z=0
clumpy cold flows shocked
Halo Mass: 4e10 2e11 1e12 3e12
Brooks et al in prep.

32. Accretion of different components in L* Galaxies Stars
accreted
as stars
form part of
the bulge.
(thick disk
faint)
Late
accretion
forms
disks

33. Conclusions