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Structure Formation: Bright side of the Universe

Anatoly Klypin New Mexico State University

Also: Stefan Gottloeber (Astrophysikalisches Institut Potsdam) Gustavo Yepes (UAM, Madrid)


Cosmological n-body+hydro simulations Codes:
SPH + TREE AMR + shock capturing hydro Physical processes: Compton cooling/heating on CMB Radiative gas cooling Star formation with simple approximations Metal enrichment Energy/momentum feedback from young stars and SN


Physics of forming galaxies
Small galaxies: cold flows Large galaxies: hot accretion

10Mpc: only the central region has high resolution


Credits: Kravtsov

100pc resolution Z=4

100 kpc scale Gas density

1 Mpc scale

Tgas


QuickTime TM a nd a YUV4 2 0 cod e c d eco mpr esso r a re nee d e d to se e this p i cture .


Galaxies too concentrated. Bulge/Disk 1:3 or higher.

Governato

3 10^12 solar masses Governato et al. 04

8 10^11 solar masses

Abadi et al 03

Peak velocity higher than in the real Milky Way. No realistic feedback yet!


Improved resolution and more realistic stellar feedback makes more realistic galaxy models.
Main test: rotation curves should be flat.
Models on the right are better than they used to be, but still there are some defects in the central regions

Governato, Mayer, Brook 2008
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Outflows: physics
High velocities are not created inside the regions of star formation: rms velocity in molecular clouds is 1-10 km/s

Young stellar cluster -> superbuble -> accelerated shock
4 kpc 10 pc

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Modeling ISM: 12 pc resolution

Early stages of evolution: first star cluster dumps its energy

Wave accelerates on declining density

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4 kpc.

12pc resolution Thin slices

Ceverino & Klypin 2007

Simulations of a Fragment of ISM

Plane of disk

1 kpc

Orthogonal to the Disk plane

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Tasker & Bryan 2008: Isolated MW. 50 pc resolution

210 kpc

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ISM and galaxy formation

· Efficiency of star formation: mass consumption should be low

· Efficiency of star formation: energy release should be high
· Angular momentum: flat rotation curves + thin stellar disks · Observed vis. modeled Outflows of gas from galaxies: velocities, metallicites, QSO absorption lines


implementation of different physical processes
Ceverino & Klypin 2007
Kravtsov's ART hydro code: Physical processes included:
AMR shock capturing hydro metallicity-dependent cooling + UV heating (Haardt & Madau). CLOUDY. Compton cooling Temperature range for cooling: 102K -108K Jeans length resolved with 4 cells Energy release from stellar winds+ SNII +SNI Thermal feedback: most * form at T< 1000K n>10cm-3

·

Runaway stars:

massive stars move with exp(-v/17km/s)

Effective =2-20 Myrs

=150-1000 Myrs

Mass consumption rate per free-fall time averaged over gas "molecular" gas (n>30cm-3) is 0.03

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Cosmology: formation of MW galaxy

Cold Flow regime

z=3.5 Major progenitor. 45 pc resolution Face-on view SFR =10Msun/year Ceverino & Klypin 2007 ART N-body+hydro code (Kravtsov) 400 kpc proper

Slice of gas density

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Ceverino & Klypin 2007

z=3.5 Major progenitor of MW. 45 pc resolution Face-on view 100 kpc proper

Stars

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z=1.3

Major progenitor of MW. 45 pc resolution

Face-on view

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Ceverino & Klypin 2007

z=3.5 Major progenitor of MW. 45 pc resolution Face-on view 400 kpc proper

Cold Flow regime

Slice of temperature

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Ceverino & Klypin 2007

350kpc

Z=2.5
40pc resolution. Mvir(z=0)=1.e12Msun. Ndm=400K


Ceverino & Klypin 2007

z=3.5 Major progenitor of MW. 45 pc resolution Face-on view 400 kpc proper

Cold Flow regime

Vmax =1000km/s

Slice of gas velocity:
Log scale in km/s

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Ceverino & Klypin 2007

z=3.5 Major progenitor of MW. 45 pc resolution Face-on view 400 kpc proper

Cold Flow regime

Slice of gas metallicity

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Flat rotation curves are still the most sensitive test for feedback models Combination of resolution and feedback improves the rotation curves
Ceverino & Klypin 2007 Resolution 45 pc. Thermal stellar feedback + runaway stars

z=3.2 MW z=1 Dwarf

Vc

irc

Vdm

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600kpc 70kpc

z=1

Disk galaxy: edge-on




Galaxies in numerical simulations





Guedes et al 2011: Milky Way model
Optical/UV Neutral H


Guedes et al 2011: Milky Way model

Milky Way z=0

z=1

stars gas


Guedes et al 2011: Milky Way model


Recent progress:

·

"galaxies" lay on the Tully-Fisher relation: no problems with angular momentum Merging of two spiral galaxies (may) produce a spiral galaxy with very large disk. Barred "galaxies" are typical.

Physics and numeresolution is 100-300pc - still too low. Requires rics: typical
subgrid physics: reduced cooling rates in places of star formation Goals: get to 20-50pc and to include some physics of molecular clouds. No subgrid physics (on its way: Kravtsov & Gnedin(Chicago), Ceverino (NMSU) Correct physics of ISM is important for forming realistic galaxies


Conclusions
· Galactic Outflows are produced by forming galaxies: put it in right regime, it flies like a bird · Velocities: 300-500 km/s are typical at z=2-3. Large (1000-2000 km/s) outflows happen frequently. · Direction of outflows: ­ perpendicular to disk at small distances (10~kpc); ­ uncorrelated with disk at larger distances. Not random: outflows find holes in density field)

· Small galaxies tend to have larger velocities given sufficient SFR (Dekel & Silk again)
· Do not violate laws of physics simulating outflows. It is tempting, but do not do it. · Need to fulfill two conditions to have feedback efficient to produce out flows: ­ overheating regime ­ high resolution: better 50 pc · Mechanism for efficient feedback has important bottleneck: young stellar cluster => superbubble · Accelerating shocks · Two important tests for any design of feedback: ­ Flat rotation curves of galaxies (thin disks in spirals) ­ QSO absorption lines

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