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Explore the formation of galaxies, clusters, and voids in the universe, including color bimodality and density fluctuations. Learn about dark matter, redshift surveys, and the evolution of structures from small peaks to superclusters. Follow the cosmic history and deep space observations, revealing the intricate process of galaxy evolution and the significant role of dark matter halos.
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Lecture 20-21: The Formation of Structure---Galaxies, Clusters, Voids Astronomy 5: The Formation and Evolution of the Universe Sandra M. Faber Spring Quarter 2007 UC Santa Cruz
We are here 1/4 of visible universe A redshift survey: 220,000 galaxies Each small dot is a galaxy
4 billion light years Milky Way galaxy Radius of cosmic horizon; 14 B lyr
4 billion light years Milky Way galaxy Radius of cosmic horizon; 14 B lyr
We are here 1/4 of visible universe A redshift survey: 220,000 galaxies Each small dot is a galaxy
Density along a line in the early Universe: Large cluster Small group Isolated galaxy Void The seeds of galaxy and structure formation are small density fluctuations that were created by inflation The highest peaks collapse first, making small proto-galaxies. Then lower peaks collapse to make galaxies, and finally clusters and superclusters.
A chunk of the Universe first expanding and then collapsing. Dark matter only. Redshift, z Scale factor a = 1/(1+z). So Universe starts out 1/50th of present size.
Now the viewpoint steps back as the Universe expands to show detail inside the cube. The expansion seems to disappear, but this is an effect of the presentation. Dark matter only.
A thin slice through the cube. Still dark matter only. Simulation courtesy of Springel, White, and Hernquist
Measles on the CMB map are the seeds of voids and superclusters. Ripples in the CMB intensity on the celestial sphere, as mapped with the WMAP satellite. The celestial sphere as portrayed from outside. The Milky Way is at the center of the sphere.
Cosmic history in 4 easy steps Graphics from WMAP team
Ultradeep field detail Near Near Far Far ???
DEEP2 looks 2/3 of the way back to the Big Bang The DEEP2 Survey has gathered spectra of 50,000 galaxies using the DEIMOS spectrograph on the Keck 2 telescope. The typical galaxy is at z = 0.9 and is 100 times fainter than galaxies in low-redshift surveys like SDSS and 2dF.
Lumps continually collide to make bigger lumps. Hierarchical clustering. Simulation courtesy of Springel, White, and Hernquist
Our matter makes up only a tiny fraction of galactic mass. The remainder is in a halo of dark matter roughly 10 times as big and 10 times as massive.
Visible galaxies embedded in the dark matter filaments Formed stars