Toward a tomographic analysis of the cross-correlation between Planck CMB lensing and H-ATLAS galaxies

We present an improved and extended analysis of the cross-correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck mission data and the high-redshift galaxies detected by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range zph ≥ 1.5. We compare the results based on the 2013 and 2015 Planck datasets, and investigate the impact of different selections of the H-ATLAS galaxy samples. Significant improvements over our previous analysis have been achieved thanks to the higher signal-to-noise ratio of the new CMB lensing map recently released by the Planck collaboration. The effective galaxy bias parameter, b, for the full galaxy sample, derived from a joint analysis of the cross-power spectrum and of the galaxy auto-power spectrum is found to be b=3.54-0.14+0.15. Furthermore, a first tomographic analysis of the cross-correlation signal is implemented by splitting the galaxy sample into two redshift intervals: 1.5 ≤ zph < 2.1 and zph ≥ 2.1. A statistically significant signal was found for both bins, indicating a substantial increase with redshift of the bias parameter: b=2.89 ± 0.23 for the lower and b=4.75-0.25+0.24 for the higher redshift bin. Consistent with our previous analysis, we find that the amplitude of the cross-correlation signal is a factor of higher than expected from the standard ΛCDM model for the assumed redshift distribution. The robustness of our results against possible systematic effects has been extensively discussed, although the tension is mitigated by passing from 4 to 3σ. © 2016. The American Astronomical Society. All rights reserved.