Evolution of the Universe
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Revision as of 21:38, 25 September 2014
Direct Cosmological Simulations of the Growth of Black Holes and Galaxies
This timelapse shows the distribution of matter in a simulated universe on large scales. The computer simulation was carried out using the cosmological hydrodynamic simulation code P-Gadget on facilities provided by the Moore Foundation in the McWilliams Center for Cosmology at Carnegie Mellon University. Simulation and visualization by Yu Feng (CMU), Tiziana Di Matteo (CMU), Rupert Croft (CMU), Volker Springel (Heidelberg Institute for Theoretical Studies), Nishikanta Khandai (CMU), Anirban Jana (Pittsburgh SuperComputing Center), Jeff Gardner (University of Washington). GigaPan conversion by Yu Feng, Randy Sargent, Chris Bartley and Paul Dille (CMU).
The density of matter is shown on a false color scale, with the densest regions in yellow and the least dense in red and black. Unlike images of the real Universe seen through optical telecopes, in the simulated image it is possible to see the filmentary structures that stretch through the space between galaxies. These structures contain mostly hydrogen and helium gas. The only luminous matter is in galaxies, which are much sparser. To see these, we need to move forward in time to the universe at late times (when stars have formed) and zoom in. Then small blobs of gas become apparent with white points (stars) in them, and dark blue gas (which signifies gas that is actively forming stars). These blobs of gas and stars are whole galaxies, and there are several thousand of them in this image, a hundred or so the size of the Milky Way and many much smaller. At high zoom levels, we can also see green circles- these represent supermassive blackholes which have formed, the circle size being proportional to black hole mass. In the real Universe we see that all large galaxies have supermassive black holes at their centers. The Milky Way, for example contains one with a mass two million times that of the Sun.
As the universe evolves from early times (it starts at an age of 10 million years after the Big Bang) the initially small fluctuations grow through the action of gravity until in the last frame (which represents the universe 14 billion years later, at redshift z=0, the present day) there are large clusters of galaxies present with vast, mostly empty spaces in between. The full image is 260 comoving Megaparsecs in width, which corresponds to a size of 850 million light years at the end of the simulation (the last frame). Because the Universe is expanding, the simulation is actually also expanding, so that the physical size of the first frame, at a redshift of 150 is only 6 million light years. The relationship between comoving Megaparsec and millions of light years is x comoving Mpc = (x *3.26 )/(1+z) Mly, where z is the redshift.
To carry out the simulation the equations of gravity, hydrodynamics, radiative cooling, and models for star formation and black hole growth were solved in parallel on a system of 100 million particles. The ingredients that make up the universe are dark matter, dark energy (in the observed proportions), 4% of normal (atomic) matter, and small initial fluctuations created during the inflationary epoch when the whole of the presently observed universe was smaller than the size of an atom.
Work supported by the National Science Foundation, award OCI-0749212, the Moore Foundation, and the Bruce and Astrid McWilliams Center for Cosmology at Carnegie Mellon University.
Watch a time warp of
Watch a time warp of
Watch a time warp showing the location of
Watch a time warp showing where theform in the simulation.