University of Waterloo
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
Phone: (519) 888-4567 ext 32215
Fax: (519) 746-8115
Professor, Department of Physics
The cosmic microwave background (CMB) probes the history of the universe in a myriad of ways.
The Atacama Cosmology Telescope (ACT) is a 6 m telescope specifically designed to measure the CMB at millimeter wavelengths. ACT has an angular resolution of better than 1.4', which means it measures not only the primordial fluctuations in the CMB (tracing the seeds of large scale structure), but is also sensitive to the intervening universe in several ways. Since its receiver measures the polarized fraction of the CMB, ACT is also able to look for the signature of gravitational waves in the CMB. ACT observes from a site at 5300 m in the Atacama Desert in Chile. This midlatitude site allows ACT to map regions of the sky in which there exist substantial data from surveys at other wavelengths. ACT detects clusters of galaxies through their Sunyaev-Zeldovich effect (a spectral effect due to scattering off the hot electrons in the clusters). ACT measures clusters directly, in blind surveys, and also makes statistical measurements based on stacking analyses and by measuring the 3-point function in the maps. Furthermore, gravitational lensing by all the intervening matter from the primordial epoch to now leads to signatures in the 4-point functions in the ACT maps. Cross-correlating the ACT lensing deflection field with other optical surveys in the same region is a particularly fruitful way of deriving cosmological information on the dynamics of the universe, namely its expansion history.