The First Direct Measurement of Gravitational Potential Decay Rate at Cosmological Scales and Improved Dark Energy Constraint

Abstract

The integrated Sachs–Wolfe (ISW) effect probes the decay rate (DR) of large-scale gravitational potential and therefore provides a unique constraint on dark energy (DE). However, its constraining power is degraded by the ISW measurement, which relies on cross-correlating with the large-scale structure (LSS) and suffers from uncertainties in galaxy bias and matter clustering. In combination with lensing-LSS cross correlation, DR can be isolated in a way free of uncertainties in galaxy bias and matter clustering. We applied this proposal to the combination of the Data Release 8 galaxy catalog of DESI imaging surveys and Planck cosmic microwave background maps. We achieved the first DR measurement, with a total significance of 3.2 σ . We verified the measurements at three redshift bins ([0.2, 0.4), [0.4, 0.6), [0.6, 0.8]), with two LSS tracers (the “low-density points” and the conventional galaxy positions). Despite its relatively low signal-to-noise ratio, the addition of DR significantly improves dark energy constraints, over Sloan Digital Sky Survey baryon acoustic oscillation (BAO) data alone or Pantheon supernovae (SNe) compilation alone. For flat w CDM cosmology, the improvement in the precision of Ω m is a factor of 1.8 over BAO and 1.5 over SNe. For the DE equation of state w , the improvement factor is 1.3 over BAO and 1.4 over SNe. These improvements demonstrate DR as a useful cosmological probe, and therefore we advocate its usage in future cosmological analysis.