Probing The Effects Of A Mixed Dark Matter Scenario Using Weak Gravitational Lensing And Cosmic Microwave Background Observations PDF Download

The cosmic microwave background (CMB) provides a backlight that allows us to probe structure out to the last scattering surface. We exploit observations of the sky at microwave and sub-mm wavelengths to measure properties of galaxies and galaxy clusters, as well as to search for possible pre-inflationary signals. In Chapters 2--4 we measure the correlation between the dark matter distribution and the microwave and sub-mm emission from galaxies to probe the connection between dark and luminous matter at redshifts ~1-3. CMB photons are gravitationally deflected by dark matter overdensities, with the majority of the ~3 arcminute RMS deflection occurring between redshift 2 and 3. The dark matter structures that lens the CMB are traced by dusty star-forming galaxies that emit strongly in the infrared, and have a redshift distribution that peaks between redshift 1 and 3. We use observations of the CMB from the Planck satellite to reconstruct the deflection angles with statistical estimators, and we correlate the deflections with observations of the infrared background light at 100-850 GHz. We find that the two signals are strongly correlated, with a correlation coefficient of approximately 0.8, and we use the measured cross spectrum to estimate the minimum mass scale at which dark matter halos host a CIB source, as well as the star formation rate density in three redshift bins between redshift 1 and 7. In Chapter 5 we use the Doppler shift of CMB light scattered by moving galaxy clusters, known as the kinetic Sunyaev-Zeldovich (kSZ) effect, to put a limit on the large-scale velocity distribution of a sample of galaxy clusters observed in WMAP CMB data. On 100 Mpc scales cluster velocities relative to the CMB are expected to be small, originating from gravitational instabilities. Larger motions could be generated by pre-inflationary inhomogeneities that leave a "tilt" across our horizon, resulting in a uniform matter flow across the horizon. The kSZ effect is sensitive to such a flow, and we use it to constrain the radial and dipole velocity of a sample of 736 clusters with mean redshift 0.12, finding no evidence for either. In Chapters 6 and 7 we search for a possible pre-inflationary signal in CMB data. Models of inflation suggest that our current patch of the universe could have been created as a nucleation bubble from a phase of false vacuum eternal inflation. If additional bubbles are produced, then it is possible that one of them intersected our past lightcone at the time of decoupling, imprinting a disk-shaped signal in the CMB. We have searched for this signal in the WMAP data using optimal algorithms that evaluate the exact posterior likelihood in an efficient and computationally fast way. We find no evidence for the signal, and place limits on the curvature perturbation generated by a collision intersecting the last scattering surface.