Galaxy speed control; investigating intrinsic alignment of galaxies with the large scale velocity field

Abstract

In this thesis the intrinsic alignment effect of the correlation between shapes of galaxies and the velocity field on large scales is investigated. As it could be additional to the probes that exist to look at the large scale structure of the universe. The large scale structure can give valuable information about the formation and evolution of the universe which can help improve the cosmological model. The velocity-shape correlation is already investigated in simulations, giving promising results. The prediction done in this thesis is on the measurability of the correlation with the data from upcoming galaxy surveys such as the LSST survey. This prediction gave a fractional error for the alignment strength of 0.022 compared to 0.0011 for the already measured galaxy density-shape correlation. The signal to noise ratio for this correlation is 263 compared to 349. The same is done for the spectroscopic 4MOST survey to get around weak lensing contamination. The fractional error for the alignment strength is 0.11 for the velocity-shape correlation compared to 0.058 for the galaxy-shape correlation. The signal to noise ratio is for this survey respectively 55 and 101. This can be interpreted as promising for the measurability of velocity-shape correlation. Also the improvement that this correlation could bring on three applications is discussed. From theoretical point of view it seems that adding velocity-shape correlation could improve on constraining observational selection effects that arise trying to extract cosmological information from the clustering of galaxies. A rough prediction on using multiple shape estimates to determine the scale dependence of the alignment model on small scales, points to an improvement after implementing this correlation. The effect of implementing velocity-shape correlation to better constrain primordial anisotropic non-Gaussianity after an estimate does not seem to give any enhancement. Although the comparison with existing results is not that straight forward to make.