Cosmic magnification on high-redshift submillimeter galaxies

TL;DR

This review consolidates the theory and observations of cosmic magnification using high-redshift submillimeter galaxies as background sources, enabled by Herschel surveys. It articulates the magnification bias and its observable cross-correlation with foreground tracers, formalized via the halo model and galaxy–matter cross-power spectrum, and details a methodology based on Landy–Szalay estimators and bootstrap covariances. The synthesis shows that wide-bin and tomographic analyses with GAMA/H-ATLAS data yield cosmological constraints compatible with LCDM, notably on $\\Omega_m$ and $\\sigma_8$, while highlighting sensitivity to sampling variance (e.g., the G15 region) and the need for larger SMG surveys and simulations. The work argues that cosmic magnification is a competitive independent probe that can be strengthened by future surveys, improved redshift calibration, and joint analyses with clustering information.

Abstract

Weak lensing magnification probes the correlation between galaxies and the underlying matter field in a similar fashion to galaxy-galaxy lensing shear. Although it has long been sidelined in favor of the latter on the grounds of a poorer performance in terms of statistical significance, the provision of a large sample of high-redshift submillimeter galaxies by the \emph{Herschel} observatory has transformed the landscape of cosmic magnification due to their optimal physical properties for magnification analyses. This review aims to summarize the core principles and unique advantages of cosmic magnification on high-redshift submillimeter galaxies and discuss recent results applied for cosmological inference. The outlook and challenges of this observable are also outlined, with a focus on the ample scope for exploration and its potential to emerge as a competitive independent cosmological probe.

Figures (5)

• Figure S1: Schematic representation of magnification bias. While the flux boosting effect raises the observed number counts of background sources, the solid angle dilution reduces them, creating a mismatch with respect to the intrinsic number counts.
• Figure S2: GAMA/H-ATLAS cross-correlation data. The grey data points show the measurements from the "tile-and-average" approach used in GON21, while the black and red data depict the single-measurement strategy using all fields and exlucding the G15 region, respectively CUE24a. This figure has been modified with respect to the original source by CUE24a.
• Figure S3: Posterior distributions of $\Omega_m$ and $\sigma_8$ from CUE24a after marginalization over the rest of parameters. Black and red plots denote the results using all four GAMA/H-ATLAS regions and excluding G15, respectively. This figure has been modified with respect to the original source by CUE24a.
• Figure S4: GAMA/H-ATLAS cross-correlation data in the tomographic setting. The blue data points depict the measurements in each of the four lens redshift bins chosen by BON24, namely $z_f\in[0.1,0.2]$, $[0.2,0.3]$, $[0.3,0.5]$ and $[0.5,0.8]$. The single-bin data from CUE24a are shown in black for comparison. This figure has been modified with respect to the original source by BON24.
• Figure S5: Halo mass function predictions from the two- (teal) and three-parameter (orange) Sheth & Tormen models using the GAMA/H-ATLAS cross-correlation in the tomographic setup CUE22. Bold and faint errorbars depict 68% and 95% credibility, respectively. The Sheth & Tormen best fit by despali16 using numerical simulations is shown as the black solid line. This figure has been modified with respect to the original source by CUE22.