Cosmology with the submillimetre galaxies magnification bias

Abstract

Context. High-z submillimetre galaxies can be used as a background sample for gravitational lensing studies thanks to their magnification bias. In particular, the magnification bias can be exploited in order to constrain the free parameters of a halo occupation distribution (HOD) model and some of the main cosmological parameters. A pseudo-tomographic analysis shows that the tomographic approach should improve the parameter estimation. Aims. In this work the magnification bias has been evaluated as cosmological tool in a tomographic set-up. The cross-correlation function (CCF) data have been used to jointly constrain the astrophysical parameters M min , M 1 , and α in each of the selected redshift bins as well as the cosmological parameters Ω M , σ 8 , and H 0 for the lambda cold dark matter (ΛCDM) model. Moreover, we explore the possible time evolution of the dark energy density by also introducing the ω 0 , ω a parameters in the joint analysis ( ω 0 CDM and ω 0 ω a CDM). Methods. The CCF was measured between a foreground spectroscopic sample of Galaxy And Mass Assembly galaxies and a background sample of Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) galaxies. The foreground sample was divided into four redshift bins (0.1–0.2, 0.2–0.3, 0.3–0.5, and 0.5–0.8) and the sample of H-ATLAS galaxies has photometric redshifts > 1.2. The CCF was modelled using a halo model description that depends on HOD and cosmological parameters. Then a Markov chain Monte Carlo method was used to estimate the parameters for different cases. Results. For the ΛCDM model the analysis yields a maximum posterior value at 0.26 with [0.17, 0.41] 68% C.I. for Ω M and at 0.87 with [0.75, 1] 68% C.I. for σ 8 . With our current results H 0 is not yet constrained. With a more general ω 0 CDM model, the constraints on Ω M and σ 8 are similar, but we found a maximum posterior value for ω 0 at −1 with [ − 1.56, −0.47] 68% C.I. In the ω 0 ω a CDM model, the results are −1.09 with [ − 1.72, −0.66] 68% C.I. for ω 0 and −0.19 with [ − 1.88, 1.48] 68% C.I. for ω a . Conclusions. The results on M min show a trend towards higher values at higher redshift confirming recent findings. The tomographic analysis presented in this work improves the constraints in the σ 8 − Ω M plane with respect to previous findings exploiting the magnification bias and it confirms that magnification bias results do not show the degeneracy found with cosmic shear measurements. Moreover, related to dark energy, we found a trend of higher ω 0 values for lower H 0 values.

Topics & Concepts