PhD Thesis Defenses, 2020
James Lasker: "Determination of the Volumetric Type Ia Supernova Rate Using the Full 5 Year Dark Energy Survey Photometrically Classified Sample"
September 24, 2020 | 1:00 PM | Zoom Room (online)
Scientific Advisor: Joshua A. Frieman

Abstract: Type Ia Supernovae are the premier high-redshift cosmological distance indicators, yet we still don't know how they are formed. One method of learning about the origin of these standard candles is to measure how often they explode and the evolution of that rate with cosmic time. The recently completed Dark Energy Survey (DES) has observed more than 3000 supernovae over 5 years, a sample which I employ here to make the most accurate single-sample power law rate measurement to date. In this thesis defense, I present the determination of the type Ia supernova rate with the DES data sample using a novel method involving no spectroscopic redshift or supernova type information. This analysis lays the groundwork for a future analysis to determine the delay times between star formation and supernova explosions to elucidate the progenitor systems that form type Ia supernovae.

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KICP Members: Joshua A. Frieman
KICP Students: James Lasker

September 28, 2020 | 5:00 PM | Zoom Room (online)
Scientific Advisor: John E. Carlstrom

Committee members: John Carlstrom, Bradford Benson, Daniel Holz, Paolo Privitera

Abstract: The cosmic microwave background (CMB) provides a method to map the universe's matter through gravitational lensing deflections as the CMB photons travel through the large-scale structures of the universe. Gravitational lensing induces correlations between CMB temperature and polarization modes at different angular scales. These correlations can be extracted by lensing quadratic estimators to reconstruct the projected 2D lensing potential and matter distribution. The power spectrum of the lensing potential is a powerful probe of the growth of structure and can constrain the sum of neutrino masses, dark energy, and the amplitude of matter density fluctuations. Furthermore, the matter distribution from lensing provides a promising source for cross-correlation with surveys at other wavelengths and offers a template for removing lensing-induced contamination in searches for inflationary gravitational waves. The third-generation camera for the South Pole Telescope (SPT-3G) is an excellent instrument for CMB lensing measurements with one arcminute resolution and high sensitivity powered by a ten-meter primary mirror and a new multichroic receiver with 16,000 polarization-sensitive detectors. A compact Fourier-Transform spectrometer (FTS) was designed and constructed for detector characterization. I review the SPT-3G instrument with emphases on the detectors and FTS, and present measurements of the lensing potential and lensing power spectrum from the 2018 data of the SPT-3G survey.

Zhaodi will be a Maria Goeppert Mayer Fellow at Argonne National Laboratory.

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KICP Members: John E. Carlstrom
KICP Students: Zhaodi Pan

October 15, 2020 | 2:00 PM | Zoom Room (online)
Scientific Advisor: John E. Carlstrom

Committee members: John Carlstrom (chair), Bradford Benson, Daniel Holz, Yau Wah

Abstract: Observations of the cosmic microwave background (CMB) form the pillar of our current understanding of cosmology. Maps of the temperature and polarization anisotropies of the CMB encode information about the initial conditions of the universe, its matter and energy content, and its evolution over time, setting tight constraints on the parameters of the LCDM cosmological model and probing the physics of inflation. Making these exquisitely precise measurements requires building increasingly sensitive instruments, with larger focal plane areas and ever-greater detector counts. SPT-3G is the latest CMB survey instrument to be installed on the 10-meter South Pole Telescope, utilizing both a larger focal plane and multichroic pixels to raise the detector count to ~16,000, a tenfold increase over its predecessor. SPT-3G will conduct a multi-year survey of a 1500 square degree patch of sky, producing maps with an unprecedented combination of depth and angular resolution and improving constraints on the CMB power spectrum by over an order of magnitude at small angular scales. In this thesis I describe the SPT-3G instrument, with special focus on the development and testing of the detectors. I present an analysis of data taken by SPT-3G during 2018 to produce a measurement of the E-mode polarization and temperature-polarization cross power spectrum of the CMB over the angular multipole range 300 < l < 3000, and I state the resulting constraints on cosmological parameters.

Upon completing his Ph.D., Daniel will begin as a Postdoctoral Researcher atPrinceton University working on Simons Observatory.

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KICP Members: John E. Carlstrom
KICP Students: Daniel Dutcher