The 40-Meter Telescope and the 5.5-Meter Telescope at the Owens Valley Radio Observatory are used primarily for studies of the Cosmic Microwave Background Radiation (CMB).
The 2.73 K cosmic microwave background (CMB) radiation, discovered by Penzias and Wilson (1965), is the relic of the hot phase of the Universe at the time of decoupling of matter and radiation about 300,000 years after the Big Bang and one billion years before the appearance of the most distant known quasar. Imprinted on the surface of last scattering (the “cosmic photosphere”) are small fluctuations in brightness temperature which reflect the fluctuations in matter and radiation density that eventually gave rise to the known structures in the universe - from planets and stars to galaxies and superclusters. The measurement of the spectrum and distribution of these “seed” density perturbations would provide a firm foundation for theories of structure formation. Thus, it is widely believed that the microwave background radiation holds the key to our understanding of the formation of all structure in the universe. Accurate measurements of the angular power spectrum of the CMB fluctuations can be used to measure several important cosmological parameters.
The hot intergalactic gas in clusters of galaxies can scatter photons of the microwave background radiation by the inverse-Compton process. This process, known as the Sunyaev-Zeldovich effect (SZE), reduces the apparent intensity of the CMB at low frequencies and increases the intensity at high frequencies. Images of the SZE can be used to study the structure and physical conditions of galaxy clusters. They also provide a direct measurement of the distances of clusters and can be used to measure the Hubble constant.
The Cosmic Background Imager (CBI) is a new Caltech telescope designed to image the microwave background on angular scales from 5 minutes of arc to 1 degree. It is currently making observations from a high, dry site in the Andes in northern Chile. On these angular scales, the emission from foreground galaxies and quasars can be confused with structure in the microwave background. The 40-Meter Telescope is being used to locate and measure these confusing sources so that they can be eliminated from the images made with the CBI.
For more information, see the Cosmic Background Imager web page.
The CMB brightness fluctuations are expected to be partly polarized due to Thomson scattering. The power spectrum of the polarized emission provides additional information about the conditions in the early universe and the cosmological parameters. The 5.5-Meter Telescope has been refitted in order to study the polarization of the CMB.
For more information, see the Polatron web page.
Most of the above projects are led by Professor Anthony Readhead. The Polarton project is led by Professor Andrew Lange.