Josh Gundersen | Searcharxiv

arXiv2009

Observing the Evolution of the Universe

How did the universe evolve? The fine angular scale (l>1000) temperature and polarization anisotropies in the CMB are a Rosetta stone for understanding the evolution of the universe. Through detailed measurements one may address everything from the physics of the birth of the universe to the history of star formation and the process by which galaxies formed. One may in addition track the evolution of the dark energy and discover the net neutrino mass. We are at the dawn of a new era in which hundreds of square degrees of sky can be mapped with arcminute resolution and sensitivities measured in microKelvin. Acquiring these data requires the use of special purpose telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and the South Pole Telescope (SPT). These new telescopes are outfitted with a new generation of custom mm-wave kilo-pixel arrays. Additional instruments are in the planning stages.

astro-ph.CO↗

arXiv2003

COMPASS: An Instrument for Measuring the Polarization of the CMB on Intermediate Angular Scales

COMPASS is an on-axis 2.6 meter telescope coupled to a correlation polarimeter. The entire instrument was built specifically for CMB polarization studies. Careful attention was given to receiver and optics design, stability of the pointing platform, avoidance of systematic offsets, and development of data analysis techniques. Here we describe the experiment, its strengths and weaknesses, and the various things we have learned that may benefit future efforts to measure the polarization of the CMB.

astro-ph↗

arXiv1997

UCSB South Pole 1994 CMB anisotropy measurement constraints on open and flat-Lambda CDM cosmogonies

We develop methods to account for experimental and observational uncertainties in likelihood analyses of data from cosmic microwave background (CMB) anisotropy experiments and apply them to an analysis of the UCSB South Pole 1994 (SP94) experiment. Observationally motivated open and spatially-flat $Λ$, cold dark matter cosmogonies are considered. Among the models we consider, the full SP94 data set is most consistent with $Ω_0 \sim 0.1-0.2$ open models and less so with old $(t_0 \gap 15 - 16 Gyr)$, high baryon density $(Ω_B \gap 0.0175 h^{-2})$, low density ($Ω_0 \sim 0.2 - 0.4), flat-$Λ$ models. The SP94 data do not rule out any of the models we consider at the $2σ$ level. The SP94 experiment is most sensitive to anisotropies on a somewhat larger, model-dependent, angular scale than the scale at which the window function peaks. For establishing the significance of a detection of CMB anisotropy we derive limits using the highest posterior density (HPD) prescription, since it yields smaller lower limits. Since HPD limits lead to tighter constraints on the CMB amplitude, they also provide for greater discrimination between models. Model normalizations deduced from the SP94 data subsets are mostly consistent with those deduced from the two-year COBE-DMR data, although the Ka-band data prefer a normalization $\sim 1σ$ lower than do the Q-band data, the Q and Ka + Q data favour a slightly higher normalization for the $Ω_0 = 0.1$ open model than does the DMR, and the Ka and Ka + Q data prefer a somewhat lower normalization for the older, higher $Ω_B$, low-density $Λ$ models than does the DMR.

astro-ph↗