Cosmic magnification on multi-catalogue Herschel submillimetre galaxies

TL;DR

This study leverages Herschel submillimetre galaxy catalogs to detect magnification bias beyond previous surveys, refining cosmological parameters and demonstrating the potential of SMGs as tracers for lensing studies.

Contribution

It expands the SMG sample using multiple Herschel catalogs, detects magnification bias beyond H-ATLAS, and provides improved cosmological constraints consistent with DM.

Findings

First detection of magnification bias in SMGs beyond H-ATLAS.

Combined analysis yields DM-consistent parameters: racm = 0.30^{+0.05}_{-0.07}, rac8 = 0.80 .07.

Results align better with Planck 2018 than previous non-tomographic studies.

Abstract

{Submillimetre galaxies (SMGs) are excellent background sources for magnification-bias studies, but the limited sky coverage in the submillimetre (sub-mm) band constrains their statistical power. Beyond H-ATLAS, Herschel produced additional sub-mm catalogues, though not optimised for spatial statistical lensing analyses.} {Our goal is to refine cosmological constraints from SMG magnification bias by exploiting the full sub-mm sky surveyed by Herschel.} {We expanded the SMG sample by incorporating other Herschel catalogues overlapping SDSS spectroscopic lenses. Random catalogues were generated via kernel density estimation to compute cross-correlations, and Markov Chain Monte Carlo methods were applied to infer astrophysical and cosmological parameters for each catalogue and for the combined dataset.} {We report the first detection of magnification bias in SMGs beyond H-ATLAS, reinforcing the robustness of this observable. Individual Herschel catalogues yield reasonable central values for $\Omega_m$ and $\sigma_8$, although with large uncertainties. The combined analysis, dominated by the more powerful H-ATLAS sample, gives results consistent with $\Lambda$CDM: $\Omega_m = 0.30^{+0.05}_{-0.07}$, $\sigma_8 = 0.80 (+/- 0.07)$, and $h < 0.80$, in better agreement with \textit{Planck} 2018 than previous non-tomographic studies.} {SMGs are promising tracers for magnification bias, but the narrow sub-mm coverage remains a major limitation. Wider surveys optimised for lensing would enable cross-correlations on larger scales, yielding tighter cosmological constraints.}