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Structure Formation in the Universe: Simulating Our Local Cosmic Neighborhood Yehuda Hoffman (HU) Formation of Local Universe University of kentucky (Apr 2008) Yehuda Hoffman Racah Institute of physics, Hebrew University (Jerusalem, Israel) Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 2 Cosmological Time Line Yehuda Hoffman (HU) Formation of Local Universe University of kentucky (Apr 2008)Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 3 Cosmic Microwave background: Temperature Fluctuations Slide 4 Detection of dark matter Gravitational Lensing Galaxy cluster Abell 1689 Distance 2 million Ly Gravitational lensing predicted by Einsteins general relativity The gravitational mass exceeds the mass seen in light & X-ray =====> DARK MATTER Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 5 Detection of dark energy Supernovae Type Ia Standard candles Observed magnitude vs redshift High redshift SN are fainter than expected in standard cosmologies Universe is currently accelerating =====> DARK ENERGY Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 6 Content of the Universe Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Angular Power Spectrum Slide 7 What have we learned from WMAP? The Universe is flat - Euclidian geometry The mass-energy budget of the Universe: 4.5% ordinary matter (baryons) 23% non-baryonic unknown dark matter Dark matter is cold (100-27.5)% cosmological constant ()? dark energy? All structure emerged from quantum fluctuations of the vacuum in the very early universe (10 -30 s after the Big Bang) Cocktail party remark: Everything has formed from nothing Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) CDM standard model Slide 8 Structure Formation Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) planck =(Gh/c 5 ) 1/2 10 -44 s Slide 9 Structure & Galaxy Formation Dark Matter dynamics: gravity - Newtonian, non-linear, non- dissipative Baryons dynamics: gravity, hydrodynamics, radiation physical processes: star formation, stellar feedback, cooling & heating... (sub-grid) Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 10 Primordial perturbations constitute a Gaussian random field The power spectrum (shape & normalization) is determined from the CMB: ( T / T) 10 -5 Initial Conditions Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 11 Dark matter clusters and forms bound objects (called DM halos) - GRAVITATIONAL INSTABILITY Baryons follows the gravitational pull of the dark matter Baryons cools radiatively, sinks to the bottom of the DM halos & form stars - GALAXY FORMATION Complex non-linear gravitational, hydrodynamical, radiative, star formation & stellar evolution processes determine the structural, dynamical, stellar & chemical properties of galaxies Prevailing idea: dark matter talks & baryons listen Massive numerical simulations are the main tool used to study these complex phenomena! Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 12 N-body simulations: gravity only Distribution of DM halos Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 13 Conditional Luminosity Function: (L|M)dL is the average # of galaxies in the range of L dL/2 residing in a DM halo of mass M (van de Bosch et al 2007) Slide 14 Populating DM with galaxies: 1.Identify DM halos 2.Construct the merging history of each halo 3.Apply simplified analytical recipes to model galaxy formation for each halo at any given time 4.Form galaxies in the DM halos Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) galaxies DM Millennium Simulation: N-body + Semi-analytical Modeling Slide 15 Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 16 Constrained Simulations Initial conditions - Gaussian random fields Random realization - only power spectrum is assumed Constrained realizations of Gaussian random fields - construct random realizations which obey any number of (linear) imposed constraints (Hoffman & Ribak 1991) Use observations to impose the observed universe on the initial conditions =====> Constrained Simulations (CSs) of the Local Universe Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 17 Slide 18 (~1000 cpu yrs) Slide 19 Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) Slide 20 Slide 21 Slide 22 Slide 23 Slide 24 Slide 25 Slide 26 Slide 27 Slide 28 LG: DM M33 M31 MW Slide 29 Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) MW: stars Slide 30 Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) M33: stars Slide 31 Yehuda Hoffman (HU) Formation of Local Universe University of Kentucky (Apr 2008) What have we learnt? 1.How to make DM halos 2.The distribution of dark matter 3.The Local Universe appears to be typical - near field cosmology makes sense 4.The LG in particular appears to be typical: environment, structure of MW & M31s halo Things we dont know 1.Galaxy formation 2.Luminosity function 3.Structural properties of galaxies 4.Star formation & its feed back on galaxy formation 5.Environmental dependance 6.... Constrained Simulations of the Local Universe 1.Numerical laboratory for galaxy formation experiments, done under realistic conditions 2.performing near field cosmology on the computer