1. The History of the Baryon Budget Yann Rasera Supervisor: Romain Teyssier and Jean-Pierre Chièze Horizon Project
Cosmological simulations
Analytical model
Model vs observations
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2. Cosmological Simulations
RAMSES an Adaptative Mesh Refinement code
Hydrodynamics and gravity
Cooling: primordial abundances
Heating: Haardt&Madau (1996) UV ionizing background
Star formation: Schmidt law and comoving density threshold
Serie of simulations
One very high resolution run
5123 coarse cells/5 refinement levelformal resolution !!!
350h on 256 processors up to z=2.8
Box length: 10 h-1 Mpc
Star formation time scale t*= 30 Gyr
6 high resolution runs
2563 coarse cells/5 refinement level formal resolution !!!
Box length: h-1 Mpc
Star formation time scale t*= 3 and 30 Gyr
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3. Gas density (z=3)
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4. Stellar density and age (z=3)
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5. Results (z=3) Gas density 2500h-1kpc 630h-1kpc 160h-1kpc 40h-1kpc
Age and density of stars
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6. Analytical model 4 BARYON PHASES: Diffuse gas (Ly) Hot gas in halos
Goal: Fast prediction of the baryon budget history
4 BARYON PHASES:
Diffuse gas (Ly)
Hot gas in halos
Cold gas in discs
Stars
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7. A simple analytical model
Cosmic accretion rate:
Accretion of diffuse gas (Tvir>Tmin)
Cosmic cooling rate:
Fast cooling:
Slow cooling (Bremsstrahlung):
Average over the mass function:
Star formation and cosmic winds:
Star formation rate:
Winds:
2 main physical parameters:
and
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8. Evolution of the 4 phases
Ordinary differential equations
Note:
IDL routine
avalaible
upon request
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9. Validation of the model
100h-1Mpc
10h-1Mpc
1h-1Mpc
t*=3Gyr
t*=30Gyr
RAMSES, no winds
Rasera&Teyssier 2005
Comoving density threshold
t*=2Gyr/w=3
GADGET, with winds
Springel&Hernquist 2003
Physical density threshold
3243
2163
1443
963
643
Good
estimate
of finite
mass
resolution
Simulations vs
analytical
model
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10. Influence of the 2 main parameters
t*=halo star formation time scale
Delays CSFR
w=wind efficiency
Lowers CSFR
Analytical model: fast parameter space exploration
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11. Observations vs model:SFR(z)
Elbaz compilation: Hughes et al. 1998, Steidel et al. 1999, Flores et al. 1999, Glazebrook et al. 1999, Yan et al. 1999, Massarotti et al. 2001, Giavalisco et al. 2004
Good fit: star formation time scale t* ≈ 1-5 Gyr
winds w≈ 1-3
Our favorite model (see later): t*=3Gyr/ w= 1.5
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12. Comoving stellar density: Ω*(z)
Ω* for the same parameters
IMF: Kroupa  50% of stars dead at z=0
z=0: Observed Ω* compatible with CSFR constraints
z=3: same models predicts 3 times more stars than observed!?
Problems in the model? In CSFR? In Ω*?
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13. Extragalactic Background Light
IEBL=80 nW/m2/sr from Bernstein et al. 1999, Chary&Elbaz 2001, Fixsen et al. 1998
Bolometric luminosity from Madau&Pozzetti (2000)
Similar constraints than Ω*(z=0)
IEBL(t*=3Gyr, w=1.5 )=100 nW/m2/sr
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14. Comoving cold gas density: Ωcold(z)
Damped Lyman Alpha: dust corrected by Pei et al. 1999
Constraints on the gas consumption time scale: t*/(w+1)≈1Gyr
Good agreement with our favorite model
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15. Individual average SFH
Heavens et al 2004: stellar population of galaxies (SDSS)
Large galaxies form stars earlier than small one
Fast decline of SFH for large galaxies at low z  AGN driven superwinds (AGN)?
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16. Conclusion High resolution numerical simulations + simple model
 baryon budget history in the hierarchical scenario
Cosmic rates implies:
t* ≈ 1-5 Gyr close to Kennicutt 1998 consumption time scale:
<gas /SFR>=2Gyr
w≈ 1-3 close to efficiency inferred from Martin 99 outflows
Model overestimates Ω*(z=3). Solutions? IMF?
Individual average SFR seems to imply:
Our standard parameters for galaxies
Superwinds w≈ 10 in groups. AGN?
Next step: simulations with winds and metals
Thank you for your attention and happy skiing!
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