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

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 Ωm > 0.22 at 95% CL and an upper bound σ8 < 0.97 at 95% CL (results from the zspec 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 Ωm − σ8 plane as follows: Ωm = 0.50−0.20+0.14 and σ8 = 0.75−0.10+0.07 at 68% CL.

A direct and robust method to observationally constrain the halo mass function via the submillimeter magnification bias: Proof of concept

“…The outcome of such a test was that there are no noticeable changes in the spread of the posterior distributions when significantly reducing the cross-correlation data errors. In addition, the findings of González-Nuevo et al (2021) about cosmological parameter constraints point in the same direction: increasing the number of sources in an attempt to diminish the statistical errors does not reduce the uncertainties of the results. This is probably related with the use of a single wide redshift bin and the assumption of no time evolution in the astrophysical HOD parameters.…”

“…In In this work, we use the angular cross-correlation function measured by González-Nuevo et al ( 2021) using the Tiles area for the same spectroscopic sample. We chose this particular set of measurements based on the analysis performed by González-Nuevo et al (2021), which studied the large-scale biases for different samples and tiling schemes. The measurements from the spectroscopic sample are only affected by the so called integral constraint (IC; Roche & Eales 1999), but the correction for the chosen tiling scheme is almost negligible (IC = 5 × 10 −4 ).…”

“…We propose instead the use of an observable that, given its direct dependence on the halo mass and clustering of the foreground lenses, provides a robust measurement of the HMF. This physical quantity is the foreground-background galaxy angular cross-correlation function, together with background samples of submillimeter galaxies, which we argue to be promising candidates for cosmological analysis through the magnification bias effect (González-Nuevo et al 2017, 2021Bonavera 2019;Bonavera et al 2020). We term this observable the submillimeter galaxy magnification bias.…”

Galaxy cluster mass density profile derived using the submillimetre galaxies magnification bias

“…In this respect, by comparing the CCF normalisation, we can approximately infer the average richness of previous works related to magnification bias. The CCF that is being used for cosmological analyses (González-Nuevo et al 2017;Bonavera et al 2020;González-Nuevo et al 2021;Cueli et al 2021) is measured using foreground samples built from galaxy catalogues. The values around 100 kpc are similar to the bin 1 or bin 2 measurements, which implies a richness of below 25.…”

“…These properties make SMGs promising candidates to be successfully used as a background sample for magnification bias studies, as in González-Nuevo et al (2014 where the CCF was measured with high significance, and as directly observed by Dunne et al (2020) with the Atacama Large Millimetre Array (ALMA). Moreover, the SMGs are used to investigate the halo mass, projected mass density profile, and concentration of foreground samples of quasi-stellar objects (QSOs; Bonavera et al 2019), for cosmological studies (Bonavera et al 2020;González-Nuevo et al 2021;Bonavera et al 2021) and to observationally constrain the halo mass function (Cueli et al 2021, Cueli et al, in prep. ).…”