This is a program of research activities broadly directed toward using the new ten-meter South Pole Telescope (SPT) to probe the nature of dark energy and inflation. The telescope and the initial detector array were constructed under a prior award, and science observations are starting during the austral winter 2007. This study includes support for operation of the SPT, storage and reduction of the data, and science analysis. The initial project is a four-thousand square degree survey, using the Sunyaev-Zel'dovich Effect (SZE) to detect all galaxy clusters more massive than a specific limiting value, independent of their redshift. Combining these results with optical redshifts, both currently available and yet to be observed, will place tight constraints on the equation of state of the dark energy. SPT observations will also measure fine-scale temperature anisotropies, which can determine whether a departure from exact scale invariance exists, as is predicted by the current 'standard' inflationary cosmology.
Longer-term projects include developing a new one-thousand-pixel, dual-polarization, multi-band polarimeter for the SPT, to measure the Cosmic Microwave Background (CMB) polarization anisotropy over scales of an arc-minute to several degrees. Measuring the angular power spectrum of the so-called B-mode polarization, as well as the large angular scale modes imprinted on the CMB by inflationary gravitational waves generated in the first instants of the Universe, exploits the unique and powerful capabilities of the SPT for research at the cutting edge of cosmology and astrophysics. The critical questions, and recommendations for research programs to help answer them, have been the focus of several national reports, including the 2000 NRC Decadal Report on Astronomy and Astrophysics, the NRC report Connecting Quarks with the Cosmos, the OSTP inter-agency report Physics of the Universe, and the reports of the Task Force on CMB Research and the Dark Energy Task Force. The science of the SPT research projects is at the heart of cosmology, is directed at answering some of these most compelling questions, and will have significant broader impacts throughout cosmology and physics.
More broadly, the project contributes to the training of the next generation of scientists by integrating graduate and undergraduate education with technology and instrumentation development, astronomical observations, and scientific analysis. The SPT surveys will also lead to large, publicly available datasets. The sharing of forefront research with non-scientists extends beyond the university to both established and new programs based on exploiting the growing popularity of video and audio content on the web. The International Polar Year celebration also offers a special opportunity to contribute to public awareness of polar science.
The South Pole Telescope (SPT) is a 10 meter diameter telescope optimized for low-noise, high-resolution imaging surveys of the sky at millimeter and submillimeter wavelengths. All aspects of the SPT — the site, the telescope, the shielding, and the cryogenic receivers — have been optimized for making ultra-sensitive measurements of the anisotropy in the 14 billion year old fossil light from the big bang, i.e., the cosmic microwave background (CMB), from degree to arcminute angular scales over thousands of square degrees of the sky. The research we are pursuing with the SPT addresses some of the most basic and compelling questions in science: What is the Universe made of? What is the fate of the Universe? What is dark energy? What are the neutrino masses? Is General Relativity the correct description of our Universe? When did the first stars and structures form? Over period supported by this award, we used a state-of-the-art superconducting kilo-pixel detector array cooled to 1/4 of a degree above absolute zero to make detailed images of the CMB over 1/16th of the sky. These images provide detailed information on the conditions in the early universe and reveal the seeds of the structures that we see in the universe today. Analysis of the data has led to precision constraints on the primordial fluctuations, the number of neutrinos and their masses, limits on early dark energy models, and increased precision of the parameters of the Lambda Cold Dark Matter (LCDM) cosmological model. The data also allow us to trace the growth of structure in the universe directly through small "secondary" perturbations to the cosmic microwave background. The SPT was used, for example, to detect the faint shadows against the cosmic microwave background (the Sunyeav-Zel’dovich effect) caused by the most massive objects in the universe, clusters of galaxies. The data also allowed us to measure spatial distortions in the maps of the background caused by the gravitational lensing — bending of light — by structure in the universe as the light makes it 14 billion year trip to reach us. The SZ and gravitational lensing measurements allow us to explore the growth of structure in the universe and thereby test models for the mysterious dark energy. In 2012 we deployed a new polarization sensitive superconducting detector array. This has been used to measure the intrinsic polarization of the cosmic microwave background — a measure of the dynamics in the early universe — as well as the so-called B-mode polarization caused by the gravitational lensing described above. The polarization data will allow increased precision measurements and tests of the cosmological model as well as a direct probe of the gravitational waves from the first instants of the universe at enormously high energies. The SPT surveys also fills a unique role as the only large-area surveys currently capable of detecting significant numbers of faint distant galaxies at mm wavelengths. A remarkable and unanticipated result was the discovery of large numbers of strongly massive, dusty galaxies that make up the high-redshift component of the cosmic infrared background light and are crucial to our understanding of massive galaxy formation. The large area of the SPT survey and its high sensitivity make it ideal for detecting and spectrally identifying the brightest such galaxies in the universe, which are preferentially high-redshift sources that have been gravitationally magnified by massive galaxies that lie along the line of sight. By identifying these important and rare sources, the SPT is an important complement to the high spatial and spectral resolution of the international Atacama Large Millimeter/submillimeter Array (ALMA), which is used to obtain high-resolution imaging of the SPT discovered lensed galaxies. These observations are giving a unique window into star formation soon after the first stars formed, roughly 13 billion years ago. With ALMA, the lensed structures will also be useful as probes of the dark matter distribution in the foreground elliptical galaxy lenses, to characterize mass distributions, substructure abundance, and determine the mass-to-light ratio in elliptical galaxies. The majority of the work on the project, from the development and building of the instrumentation, to the observing, data reduction and scientific analysis is performed by graduate students and post doctoral researchers. In addition to being trained in all aspects of state-of-the-art instrumentation and data analysis, they are able to participate in a broad range of education and outreach activities. Their technical and communication training well prepares them for pursuing their career choices, whether in industry or academia.
