Accelerated expansion of the universe and chasing photons from the CMB to study the late time integrated Sachs-Wolfe effect over different redshift ranges

In this study, we are going to discuss the accelerated expansion of the universe and how this accelerated expansion affects the paths of photons from cosmic microwave background radiation (CMB). Then we will see how wide-field galaxy surveys along with cosmic CMB anisotropy maps can help us in studying dark energy. The cross-correlation of galaxy over/under-density maps with CMB anisotropy maps help us in measuring one of the most useful signatures of dark energy i.e. Integrated Sachs-Wolfe (ISW) effect. ISW effect explains the blue-shifting and red-shifting of CMB photons when they reach to us after passing through large scale structures and super-voids respectively. We will look into the theoretical foundations behind ISW effect and discuss how modern all sky galaxy surveys like EMU-ASKAP will be useful in studying the effect.