Joint Astrophysics Colloquium

Observations of the Cosmic Microwave Background on Small Scales

Jon Sievers

CITA

The Cosmic Microwave Background (CMB) has revolutionized our understanding of the large-scale properties of the universe. To date, most of the information in the CMB has come from large angular scales (>~20-30 arcminutes) where the CMB fluctuations are the dominant signal. On smaller scales, the signal is more complicated, with large contributions from clusters of galaxies, and radio and infrared sources. We present the final results from nearly five years of Cosmic Background Imager (CBI) observations, a radio interferometer located at 5000 meters in the Chilean Andes, which show an unexpectedly high level of power on small scales. We also discuss what we hope to learn from an upgraded CBI and the Atacama Cosmology Telescope, two experiments currently taking small-scale data.