Tomography-based observational measurements of the halo mass function via the submillimeter magnification bias

TL;DR

This study uses tomographic analysis of magnification bias on submillimeter galaxies to place observational constraints on the halo mass function, revealing discrepancies with standard simulation-based models.

Contribution

It introduces a tomographic method to improve constraints on the halo mass function from magnification bias measurements, highlighting deviations from simulation predictions.

Findings

Tomography significantly reduces uncertainties in HMF constraints.

Results suggest higher halo densities below 10^{12} M_sun/h than simulations predict.

Discrepancies with N-body simulation values are observed at 2-3 sigma levels.

Abstract

Aims. The main goal of this paper is to derive observational constraints on the halo mass fuction (HMF) by performing a tomographic analysis of the magnification bias signal on a sample of background submillimeter galaxies. The results can then be compared with those from a non-tomographic study. Methods. We measure the cross-correlation function between a sample of foreground GAMA galaxies with spectroscopic redshifts in the range $0.1 < z < 0.8$ (and divided up into four bins) and a sample of background submillimeter galaxies from H-ATLAS with photometric redshifts in the range $1.2 < z < 4.0$. We model the weak lensing signal within the halo model formalism and carry out a Markov chain Monte Carlo algorithm to obtain the posterior distribution of all HMF parameters, which we assume to follow the Sheth and Tormen (ST) three-parameter and two-parameter fits. Results. While the observational constraints on the HMF from the non-tomographic analysis are not stringent, there is a remarkable improvement in terms of uncertainty reduction when tomography is adopted. Moreover, with respect to the traditional ST triple of values from numerical simulations, the results from the three-parameter fit predict a higher number density of halos at masses below $10^{12}M_{\odot}/h$ at 95% credibility. The two-parameter fit yields even more restricting results, with a larger number density of halos below $10^{13}M_{\odot}/h$ and a lower one above $10^{14}M_{\odot}/h$, this time at more than 3$\sigma$ credibility. Our results are therefore in disagreement with the standard N-body values for the ST fit at 2$\sigma$ and 3$\sigma$, respectively.