New light on Dark Cosmos

TL;DR

The study demonstrates a statistically significant detection of the Integrated Sachs-Wolfe (ISW) effect by cross-correlating WMAP CMB temperatures with multiple galaxy surveys spanning a wide redshift range. Using a bias self-calibration framework and fixed cosmological priors, it derives constraints on the matter and dark energy densities, showing consistency with a flat ΛCDM cosmos and a dark-energy equation of state near $w=-1$. The results, combined with Type Ia supernova data, yield $\Omega_\Lambda \approx 0.70$ and $\Omega_m \approx 0.30$, with $w = -1.02 \pm 0.17$ under flatness, reinforcing the presence of dark energy and dark matter. The analysis also demonstrates robustness to selection-function uncertainties and potential contaminants, establishing ISW cross-correlation as a complementary probe of cosmic acceleration and structure growth.

Abstract

Recent studies by a number of independent collaborations, have correlated the CMB temperatures measured by the WMAP satellite with different galaxy surveys that trace the matter distribution with light from the whole range of the electromagnetic spectrum: radio, far-infrared, optical and X-ray surveys. The new data systematically finds positive correlations, indicating a rapid slow down in the growth of structure in the universe. Individual cross-correlation measurements are of low significance, but we show that combining data at different redshifts introduces important new constraints. Contrary to what happens at low redshifts, for a fixed $\Omm$, the higher the dark energy contend, $\Ol$, the lower the ISW cross-correlation amplitude. At 68% confidence level, the data finds new independent evidence of dark energy: $\Ol =0.42-1.22$ . It also confirms, to higher significance, the presence of a large dark matter component: $\Omm =0.18-0.34$, exceeding the density of baryonic matter, but far from the critical value. Combining these new constraints with the prior of a flat universe, or the prior of an accelerating universe provides strong new evidence for a dark cosmos. Combination with supernova data yields $\Ol = 0.71 \pm 0.13$, $\Omm = 0.29 \pm 0.04$. If we also assume a flat universe, we find $\Ol = 0.70 \pm 0.05$ and $w = -1.02 \pm 0.17$ for a constant dark energy equation of state.

Figures (8)

• Figure 1: Redshift dependence of $W_{ISW}(z)$ in Eq.[\ref{['final_wtg']}] for different values of $\Omega_m$ and $\Omega_\Lambda$. Bottom left, top right and top left panels shows a fixed $\Omega_m=0.5$, $\Omega_m=0.3$ and $\Omega_m=0.1$ respectively. In all cases: $\Omega_\Lambda=0.0$ (dotted blue line) , $\Omega_\Lambda=0.7$ (continuos black line) and $\Omega_\Lambda=1.0$ (dashed red line). Bottom right panel shows a fixed $\Omega_\Lambda=0.7$ and $\Omega_m=0.3$ (continuos black line), $\Omega_m=0.5$ (dotted blue line) and $\Omega_\Lambda=0.1$ (dashed red line).
• Figure 2: Redshift dependence of $W_{ISW}$ in eq [\ref{['final_wtg']}] for flat models with constant equation of state. Right panel shows a fixed $\Omega_m=0.2$ and left panel $\Omega_m=0.3$. In both cases $w=-2$ (black continuous line), $w=-1.5$ (red dashed line), $w=-1$ (green dot-dashed line), $w=-0.5$ (blue doubledot-dashed line), and $w=0$ (brown dotted line)
• Figure 3: Dependence of $W_{ISW}$ on the equation of state parameter $w$ for flat models at different redshifts and values of $\Omega_m$. $\Omega=0.3$ (back continuous lines), $\Omega_m=0.25$ (red dashed lines), $\Omega_m=0.2$ (green dotted lines). Redshifts are 0.1, 0.25, 0.5, 1.0, 1.5 from top to bottom.
• Figure 4: Symbols with error bars correspond to the different measurements $w_{TG}/b$ in Table 1. As an illustration of the shape, the continuous, short-dashed and long-dashed lines show the concordance ($\Omega_m=0.3,\Omega_\Lambda=0.7$), opened ($\Omega_m=0.3,\Omega_\Lambda=0.0$) and closed ($\Omega_m=0.3,\Omega_\Lambda=1.1$) model predictions (at $\theta=6^\circ$). The dotted line corresponds to the galaxy-galaxy prediction (and also the dust contamination model). All lines have arbitrary normalization.
• Figure 5: One, two and three sigma confidence contours in the $(\Omega_m,\Omega_{\Lambda})$ plane (marginalized over $h$) for the $\Lambda$CDM model. Top: constraints from only ISW. Bottom: constraints from SNIa (blue) and ISW (green) along with the combined contours (purple).