The High Redshift Integrated Sachs-Wolfe Effect

Understand

In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky Survey Data Release Six (SDSS DR6) of about one million photometrically selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high redshift, aiming at constraining the behavior of the expansion rate and thus the behaviour of dark energy at those epochs.

• This unique sample significantly extends previous catalogs to higher redshifts while retaining high efficiency in the selection algorithm.
• We compute the auto-correlation function (ACF) of QSO number density from which we extract the bias and the stellar contamination.
• We then calculate the cross-correlation function (CCF) between QSO number density and Cosmic Microwave Background (CMB) temperature fluctuations in different subsamples: at high z>1.5 and low z<1.5 redshifts and for two different choices of QSO in a conservative and in a more speculative analysis.