Integrated Sachs-Wolfe effect in cross-correlation: The observer's manual

The Integrated Sachs-Wolfe (ISW) effect is a direct signature of the presence of dark energy in the universe, in the absence of spatial curvature. A powerful method for observing the ISW effect is through cross-correlation of the cosmic microwave background with a tracer of the matter in the low redshift universe. In this paper, we describe the dependence of the obtained cross-correlation signal on the geometry and other properties of a survey of the low redshift universe. We show that an all-sky survey with about 10x10(6) galaxies, almost uniformly distributed within 0<z<1 should yield a near optimal ISW detection, at similar to5sigma level. In order to achieve this level of signal-to-noise, the systematic anisotropies in the survey must be below similar to0.1%, on the scale of similar to10degrees on the sky, while the systematic error in redshift estimates must be less than 0.05. Then, we argue that, while an ISW detection will not be a good way of constraining the conventional properties of dark energy, it could be a valuable means of testing alternative theories of gravity on large physical scales.