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Galaxy Formation in the Cosmic Web

The research group I work with, the University of Washington N-body shop, has made a fantastic poster about how galaxies form in the cosmic web and how we use computer simulations to understand such a complex process. We made the poster as a form of outreach and in particular for students who may be interested in astronomy research. Please feel free share or print the poster and if there is interest we may consider printing and sending out full size version of the poster for public displays. Here is the large pdf version of the poster “Galaxy formation in the Cosmic Web”.

The universe doesn’t fit in a lab; therefore, astrophysicists use super computers to simulate its history and study the complex physics driving the evolution of the galaxies within it. This poster’s image of the ‘cosmic web’ is from such a simulation. It shows the evolving gas distribution within a large patch of the Universe in the so called Cold Dark Matter scenario. In this model Dark Matter and Dark energy contribute to 95% of the mass-energy density of the Universe. Only the remaining 5% (gas and stars) can actually be seen. Our research group, the ‘N-Body Shop’, makes predictions of what astronomers will observe and ties observations to the underlying distribution of dark matter.

  1. 1-001Gravity is an attractive force causing dark  matter and gas to flow along filaments and eventually form galaxies. Galaxies like our own Milky Way form at the intersection of the largest filaments of Dark Matter and gas in the so called ‘cosmic web’. This simulation achieves such a high resolution that we can predict how many stars will form inside individual galaxies.
  2. 2-001As clusters of stars form in collapsing gas clouds, the most massive stars evolve into Supernovae, unstable stars that explode and heat their surrounding gas. During the explosion, heavy atoms fused in the center of the star such as oxygen, iron and carbon are dispersed into space. The hot gas surrounding the explosion has been observed to expand at several hundred km/sec, forming large bubbles. This gas may eventually re-collapse to form a new generation of stars. Our own Solar System formed from material previously processed by Supernovae.
  3. 3-001Galaxies as we see them today formed over billions of years. Driven by mutual gravitational attraction, individual galaxies and their surrounding dark matter halos merge, forming more and more massive systems. The largest structures in this image contain galaxies as massive as our own Milky way. Due to a continuing build up of mass, the largest dark matter halos in the present Universe contain hundreds of massive galaxies.
  4. 4-001Regions of space that are significantly under dense are called ‘voids’. These are regions where the density of matter is only 10% of the average density of the Universe, or almost a million times less dense than the density inside galaxies like our own. Almost no galaxies form in the voids, and so no hot gas is observed.
  5. 5-001These small clouds of hot gas are associated with stars forming in the smallest known galaxies, often referred to as ‘dwarfs’. The smallest dwarf galaxies form only a few hundred thousand stars and consist mostly of Dark Matter. It would take the mass of more than a thousand dwarf galaxies to make a galaxy as big as the Milky Way. The Milky Way and its nearest massive neighbor the Andromeda galaxy are each surrounded by several dozen dwarfs galaxies. Some have only been discovered in the past few years and many remain to be found, too dim to see even with powerful telescopes.

The N-Body Shop research is funded in part by grants from the National Science Foundation and the National Aeronautics and Space Administration.

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