A detection of the integrated Sachs-Wolfe effect

We have detected statistically significant correlations between the cosmic microwave background and two tracers of large-scale structure, the HEAO1 A2 full sky hard X-ray map [Boldt, E., 1987. Phys. Rep. 146, 215] and the NVSS 1.4 GHz, nearly full sky radio galaxy survey [Condon, J., et al., 1998. Astron. J. 115, 1693]. The level of correlations in these maps is consistent with that predicted for the integrated Sachs-Wolfe (ISW) effect in the context of a ΛCDM cosmological model and, therefore, provides independent evidence for a cosmological constant. A maximum likelihood fit to the amplitude of the ISW effect relative to the predicted value is 1.13 ± 0.35 (statistical error only).