MASON ASTR 302 - Universe in a box: simulating formation of cosmic structures

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Universe in a box:simulating formation of cosmic structuresAndrey KravtsovDepartment of Astronomy & AstrophysicsCenter for Cosmological Physics (CfCP)University of Chicagohttp://astro.uchicago.edu/~andrey/talks/http://cfcp.uchicago.edu/lss/GalaxiesGalaxy ClustersSupergalactic plane on the skyBranchini et al. 1998The LocalSuperclusterGerard de Vaucouleurs 1918-1995 on the skyLarge-scale structure of the Universeas seenby the CfA surveyOn even larger scales... (billions of light years)Structures in the Universegraphics from Wayne Hu (background.uchicago.edu/~whu)Formation of structuresas cosmologists envision itBig Bangz=1066First particlesformLight elements(H, He, Li)formz=100000Universe becomesneutralz=1000Galaxies formz~1-5First stars formUniverse is reionizedz~10Solar systemformsz~0.4Present dayz=0Content of the Universe: all existing components (protons, neutrons, hypothetical dark matter) contribute to gravity and can influence the rate with which the Universe expandsó The contribution of each component is measured in units of critical density: Ωi = ρ/ ρcritContent of the Universe: observational probes% Cosmic Microwave Background ripplesõ physics causing 10-5deviations from the uniform black body temperature is very well understood in a given model. Observablestatistics of fluctuations (e.g., angular correlation function or power spectrum) depend on cosmological parameters, including matter and energy content.% Large-scale structure of the Universeí galaxies, galaxy clusters, filaments% Standard "candles"ð any object whose intrinsic brightness is known or can be deduced from observations without using distance. SNIa are currently the best cosmological standard candles known% Standard rulers (systems with known intrinsic size)Cosmic Microwave Background (CMB) Temperature AnisotropiesWilkinson Microwave Anistropy Probe (WMAP) satellite resultscirca February 2003High redshift supernovae type IaSNAP satellite proposalCosmic PieComputer Simulations: How to set up and where to begin? % If the content of the Universe is assumed, theory predicts the statistical properties of inhomogeneities in matter distributionõ these predictions are used to set up initial conditions of the simulations% Simple analytic predictions are accurate only while inhomogeneities are small (<10% fluctuations with respect to the mean density of the Universe)í simulations are initialized at an epoch before analytic predictions break down, during the so-called "Dark Ages"% Numerical simulations are used to follow formation of structures and make accurate predictions at later epochs where analytic calculations break downðComputer Simulations: How do we model? % Gravity is the kingõ gravity is by far the strongest force on the large scales. gravitational interactions are modelled using Newton's laws% Other forces may need to be included depending on the composition of the Universe and scales consideredí ordinary matter, the baryons, experiences pressure forces if compressed to sufficiently high densities. these "hydrodynamic" forces are included in simulations that include baryonsWe all live inCosmological Redshift as a measure of distance and timeredshiftDistanceAge of the UniverseComputer Simulations: discretizing matter and space % Space and time are continuous on macroscopic scales, but computers can only deal with discrete numbers% Memory and CPU speed limit the number of volume elements and particles that we can simulateí in the standard theories, 1051-1082dark matter particles are expected in a cubic Megaparsecí current computers can handle only up to a billion particles í ----> need to discretizeHardwareSupercomputers at National Centers and Labs(e.g., the National Center for Supercomputer Applications -NCSA)www.ncsa.uiuc.eduLots and lots of storage...Many Many Lines of SoftwareUniverse in a Box:modelling formation of structures redshift = 10; 13 billion years agoUniverse in a Box:modelling formation of structures redshift = 5; 12.3 billion years agoUniverse in a Box:modelling formation of structures redshift = 3; 11.4 billion years agoUniverse in a Box:modelling formation of structures redshift = 1; 7.7 billion years agoUniverse in a Box:modelling formation of structures redshift = 0; today43 MpcΛCDM4 MpcΛCDMBaryons: sloshing, shocking, coolingFrom darkness to light:the messy physics of galactic kitchenTo model formation of galaxieswe need to deal with "gastrophysics"...Towards simulating realistic


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MASON ASTR 302 - Universe in a box: simulating formation of cosmic structures

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