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Hydrodynamical simulations of cosmic structures

Hydrodynamical simulations of cosmic structures. Stefano Borgani Department of Astronomy Inter-dept. Centre for Computational Sciences University of Trieste. Core group: Collaborators: SB (DAUT) Francesca Matteucci (staff, DAUT)

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Hydrodynamical simulations of cosmic structures

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  1. Hydrodynamical simulations of cosmic structures Stefano Borgani Department of Astronomy Inter-dept. Centre for Computational Sciences University of Trieste Core group:Collaborators: SB (DAUT) Francesca Matteucci (staff, DAUT) Luca Tornatore (post-doc, SISSA) Cristina Chiappini (staff, INAF) Silvia Ameglio (PhD, DAUT) Andrea Biviano (staff, INAF) Alex Saro (undergrad., DAUT) Marisa Girardi (staff, DAUT) Francesco Calura (post-doc, DAUT) Paolo Tozzi (staff, INAF) Talk @ CISC Workshop, Trieste, June 15th 2005

  2. Who are we? Basel: Ortwin Gerhard Bologna: Stefano Ettori Lauro Moscardini Mauro Roncarelli Garching: Klaus Dolag Volker Springel Trieste: Silvia Ameglio Stefano Borgani Luca Tornatore Alex Saro Beijing: Ling-Mei Cheng Padova: Giuseppe Tormen Elena Rasia Roma: Pasquale Mazzotta Torino: Magda Arnaboldi Antonaldo Diaferio Giuseppe Murante

  3. The initial conditions

  4. The final state REFLEX survey 2dF GRS

  5. What does a LSS model require? (a)Parameters of the Friedmann background (m=0.3 ; =0.7 ; H0=70+/-5 km/s/Mpc). (b) Initial fluctuation spectrum(P(k)kn with n=1). (c)Choice of fluctuation mode(adiabatic). (d)Statistical distribution of fluctuations(Gaussian). (e)Chemistry:density of baryons, cold and hot particles, number of relativistic species. (f)Tools to follow the evolution of perturbations:linear theory, approximate methods for non-linear evolution, numerical computations(N-body). (g)Relation between distributions of mass and light: evolution of gas, galaxy formation, star formation processes.

  6. The equations of motion Density fluctuation field: (a)Continuity Equation: (b)Euler Equation: (c)Poisson Equation:

  7. Evolution of hot (T> 3 keV)clusters BG ‘01

  8. N-body approaches to gravitational instability Parameters defining a simulation: 1. Box size L: ~ 1 Mpc for the formation of a single galaxy ~ 500 Mpc for the distribution of galaxies and clusters 2. Mass resolution: ~ 105-106 Msun for the formation of a single galaxy; ~108 Msun for the formation of a galaxy cluster 3. Force resolution: ~ 0.1 kpc for the formation of a single galaxy; ~ 1-5 kpc for the formation of a galaxy cluster Method 1.Direct summation Compute the force on a given particles by directly summing over the contributions of the other N-1 particles: e:softening parameter (force resolution)  N(N-1)/2 operations!!!

  9. N-body approaches to gravitational instability Method 4. Tree codes (Barnes & Hutt 1986) General strategy: Consider a far-away group of particles as a single particle for the force computation The limiting “aperture angle” =s/r regulates the accuracy of the long-range force.

  10. Smoothed particle hydrodynamics (SPH) (Monaghan 1992, ARAA, 30, 543) Use an interpolation method to express any function in terms of its values at a set of disordered points (i.e. particles): Def.: Intergral interpolant of the function A(r): W: interpolating kernel. When dealing with a discrete distribution of particles: b: particle label mb: mass of the b-th particle rb: density of the b-th particle Ab: value of A(r) at the position rb

  11. L=480 Mpc/h Ngas=NDM=4803 s8=0.8 zin=46

  12. The simulation code Tree + SPHGADGET2 (Springel et al .’01; Springel ‘05) www.MPA-Garching.MPG.DE/gadget Explicit entropy conservation (Springel & Hernquist ‘02) Radiative cooling + uniform evolving UV background Multiphase model for self-regulated star-formation Phenomenological model for galactic winds (Springel & Hernquist ‘03) Chemical enrichment from Sn-Ia and II(Tornatore et al. ’04, ‘05) Reduced-viscosity SPH scheme(Dolag et al. ‘05, in prep.)  ..... b:fraction of mass in stars>8M(Salpeter IMF) c: SN energy fraction powering winds(=0.5-1) h:amount of gas in wind, units ofdM* (=2)  vw (300-500) km s-1

  13. The simulation box(z=0) Gas density Gas temperature 40,000 CPU hours on the IBM-SP4 70 GB RAM – 1.2 TB output

  14. The biggest cluster(1.3 1015 h-1 M ) temperature field density field 9 h -1 Mpc 9 h -1 Mpc 9 h -1 Mpc

  15. Simulation of a single halo

  16. A Cluster Resimulation Champaign Extract a few (4) clusters from the box and resimulate at higher resolution Cl-2 2.9e14 M/h Cl-1 1.4e15 M/h Cl-3 2.7e14 M/h Cl-4 1.6e14 M/h

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