Cosmological constraints on the magnification bias on sub-millimetre galaxies after large-scale bias corrections

¹ Departamento de Física, Universidad de Oviedo, C. Federico Garcia Lorca 18, 33007 Oviedo, Spain
e-mail: gnuevo@uniovi.es
² Instituto Universitario de Ciencias y Tecnologías Espaciales de Asturias (ICTEA), C. Independencia 13, 33004 Oviedo, Spain
³ International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
⁴ Institute for Fundamental Physics of the Universe (IFPU), Via Beirut 2, 34014 Trieste, Italy
⁵ Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 1, Roma, Italy
⁶ INFN, Sezione di Roma 2, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 1, Roma, Italy
⁷ Departamento de Matemáticas, Universidad de Oviedo, C. Federico Garcia Lorca 18, 33007 Oviedo, Spain

Received: 27 July 2020
Accepted: 9 December 2020

Abstract

Context. The study of the magnification bias produced on high-redshift sub-millimetre galaxies by foreground galaxies through the analysis of the cross-correlation function was recently demonstrated as an interesting independent alternative to the weak-lensing shear as a cosmological probe.

Aims. In the case of the proposed observable, most of the cosmological constraints mainly depend on the largest angular separation measurements. Therefore, we aim to study and correct the main large-scale biases that affect foreground and background galaxy samples to produce a robust estimation of the cross-correlation function. Then we analyse the corrected signal to derive updated cosmological constraints.

Methods. We measured the large-scale, bias-corrected cross-correlation functions using a background sample of H-ATLAS galaxies with photometric redshifts > 1.2 and two different foreground samples (GAMA galaxies with spectroscopic redshifts or SDSS galaxies with photometric ones, both in the range 0.2 < z < 0.8). These measurements are modelled using the traditional halo model description that depends on both halo occupation distribution and cosmological parameters. We then estimated these parameters by performing a Markov chain Monte Carlo under multiple scenarios to study the performance of this observable and how to improve its results.

Results. After the large-scale bias corrections, we obtain only minor improvements with respect to the previous magnification bias results, mainly confirming their conclusions: a lower bound on Ω_m > 0.22 at 95% CL and an upper bound σ₈ < 0.97 at 95% CL (results from the z_spec sample). Neither the much higher surface density of the foreground photometric sample nor the assumption of Gaussian priors for the remaining unconstrained parameters significantly improve the derived constraints. However, by combining both foreground samples into a simplified tomographic analysis, we were able to obtain interesting constraints on the Ω_m − σ₈ plane as follows: Ω_m = 0.50_−0.20^+0.14 and σ₈ = 0.75_−0.10^+0.07 at 68% CL.