Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session C11: Invited Session: Frontiers of Computational Cosmology |
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Sponsoring Units: DCOMP DAP Chair: Paul Shapiro, University of Texas at Austin Room: Key 7 |
Saturday, April 11, 2015 1:30PM - 2:06PM |
C11.00001: Cosmological N-body Simulation of Galaxy and Large-Scale Structure Formation: The Gravity Frontier Invited Speaker: Anatoly Klypin One of the first N-body simulations done almost 50 years ago had only 200 self-gravitating particles. Even this first baby step made substantial impact on understanding how astronomical objects should form. Now powerful supercomputers and new algorithms allow astronomers produce N-body simulations that employ up to a trillion dark matter particles and produce vital theoretical predictions regarding formation, evolution, structure and statistics of objects ranging from dwarf galaxies to clusters and superclusters of galaxies. With only gravity involved in these theoretical models, one would naively expect that by now we should know everything we need about N-body dynamics of cosmological fluctuations. Not the case. It appears that the Universe was not cooperative and gave us divergencies in the initial conditions generated during the Inflation epoch and subsequent expansion of the Universe - the infinite phase-space density and divergent density fluctuations. Ever increasing observational demands on statistics and accuracy of theoretical predictions is another driving force for more realistic and larger N-body simulations. Large current and new planned observational projects such as BOSS, eBOSS, Euclid, LSST will bring information on spatial distribution, motion, and properties of millions of galaxies at different redshifts. Direct simulations of evolution of gas and formation of stars for millions of forming galaxies will not be available for years leaving astronomers with the only option - to develop methods to combine large N-body simulations with models of galaxy formation to produce accurate theoretical predictions. I will discuss the current status of the field and directions of its development. [Preview Abstract] |
Saturday, April 11, 2015 2:06PM - 2:42PM |
C11.00002: Cosmological Radiative Transfer + Hydro + N-body Simulation of Galaxy Formation and the Intergalactic Medium: The Radiation-Hydro Frontier Invited Speaker: Romain Teyssier Galaxy and star formation are two of the most important unsolved problems in modern astrophysics. Theoretical models are relying more and more on complex computer simulations, aiming at reproducing the complex properties of non-linear gravitational and gas dynamics. It has been known for a long time that radiation processes are also playing an important role in building stars and shaping galaxies. It is only recently however that radiation hydrodynamics has been introduced in the theory of star and galaxy formation, as a possible way to solve the long-standing issue of stellar feedback, and its effects on regulating star formation in giant galaxies. On larger scale, radiation hydrodynamics has also to be considered to model cosmic re-ionization, the next frontier in observational cosmology. I will describe recent advances in modelling radiation hydrodynamics effects in the context of cosmology and galaxy formation simulations, and outline some of the numerical and algorithmic challenges we have to face to prepare the future. [Preview Abstract] |
Saturday, April 11, 2015 2:42PM - 3:18PM |
C11.00003: Cosmological Hydro + N-body Simulation of Galaxy and Large-Scale Structure Formation: The Gas Dynamics Frontier Invited Speaker: Phillip Hopkins The most fundamental unsolved problems in galaxy formation revolve around ``feedback'' from massive stars and black holes. I'll present new simulations which combine new numerical methods and physics in an attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to `self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, and many observed properties of the ISM, star formation, and galaxies can be understood as a fundamental consequence of super-sonic turbulence in a rapidly cooling, self-gravitating medium. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, change the nature of dark matter cores and `cusps,' and re-structure the circum-galactic and inter-galactic medium. These winds depend non-linearly on multiple feedback mechanisms in a way that explains why they have been so difficult to model in previous ``sub-grid'' approaches. This resolves long-standing problems in understanding even apparently ``simple'' galaxy properties like the mass-metallicity relation. Finally, I'll discuss where stellar feedback fails, and additional feedback, perhaps from AGN, is really needed to explain observations. [Preview Abstract] |
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