ACT Atacama Cosmology Telescope

We describe the measurement of the beam profiles and window functions for the Atacama Cosmology Telescope (ACT), which operated from 2007 to 2010 with kilo-pixel bolometer arrays centered at 148, 218, and 277 GHz. Maps of Saturn are used to measure the beam shape in each array and for each season of observations. Observations of Uranus made regularly throughout each observing season are used to measure the effects of atmospheric opacity and to monitor deviations in telescope focus over the season. Using the WMAP-based calibration of the ACT maps to the CMB blackbody, we obtain precise measurements of the brightness temperatures of the Uranus and Saturn disks at effective frequencies of 149 and 219 GHz.

Within the ACT maps lie hundreds of galaxies.  We divide 191 galaxies into two types based on their spectral characteristics.  Most have emission dominated by synchrotron radiation, as charged particles whirl around magnetic fields in giant radio lobes created by active galactic nuclei.  The other two dozen are dust enshrouded and prodigiously star-forming.  We further characterize these galaxies through cross-identification with existing catalogs, and those without any cross-identification represent a new intriguing subpopulation.