Final PhD Oral Examination (Thesis Title: “Probing the Large-Scale Structure of the Universe with the Sunyaev-Zel'dovish Effect”)

Event Date and Time: 
Fri, 2017-09-22 12:30 - 14:30
Room 318, Hennings Building
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 

The Sunyaev-Zeldovich (SZ) effect is a spectral distortion in the Cosmic Microwave Background (CMB), due to up-scattering of CMB photons by high energy electrons in clusters of galaxies or any cosmic structure. The Planck satellite mission has measured the spectral distortion with great sensitivity and has produced a full-sky SZ (y) map, which can be used to trace the large-scale structure of the Universe.

In this dissertation, I construct the average SZ (y) profile of ~65,000Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey Data Release 7 (SDSS/DR7) using the Planck y map and compare the measured profile with predictions from the cosmo-OWLS suite of cosmological hydro-dynamical simulations. This comparison agrees well for models that include feedback from active galactic nuclei (AGN feedback).

In addition, I search for the SZ signal due to gas filaments between ~260,000 pairs of LRGs taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12), lying within 6-10 Mpc/h of each other in tangential direction and 6 Mpc/h in radial direction. I find a statistically significant SZ signal between the LRG pairs. This is the first detection of gas plausibly located in filaments, expected to exist in the large-scale structure of the universe. I compare this result with the BAHAMAS suite of cosmological hydrodynamical simulations and find that it predicts a slightly lower, but marginally consistent result.

As an extension of my MSc. thesis work, I study CMB polarization. The B-mode component of CMB polarization is an important observable to test the theory of inflation in the early universe. However, foreground emissions in our own galaxy dominates the B-mode signal and therefore multi-frequency observations will be required to separate any CMB signal from the foreground emission. I assess the value of adding a new low-frequency channel at 10 GHz for the foreground removal problem by simulating realistic experimental data. I find that such a channel can greatly improve our determination of the synchrotron component which, in turn, significantly improves the reliability of the CMB separation.

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