Cosmology in 2D: the concentration-mass relation for galaxy clusters

TL;DR

This study systematically analyzes biases in galaxy cluster mass and concentration estimates from mock lensing data, proposing correction methods to improve cosmological parameter measurements.

Contribution

It introduces correction techniques for projection effects and adiabatic contraction in the c-M relation, enhancing the accuracy of cosmological inferences from galaxy cluster data.

Findings

Halo triaxiality and substructures cause biases in mass and concentration estimates.

Knowing cluster elongation reduces mass bias but not concentration bias.

Corrected estimates enable cosmological parameter recovery within 1-sigma confidence.

Abstract

The aim of this work is to perform a systematic study of the measures of the mass and concentration estimated by fitting the convergence profile of a large sample of mock galaxy cluster size lenses, created with the publicly available code MOKA. We found that the main contribution to the bias in mass and in concentration is due to the halo triaxiality and second to the presence of substructures within the host halo virial radius. We show that knowing the cluster elongation along the line of sight helps in correcting the mass bias, but still keeps a small negative bias for the concentration. If these mass and concentration biases will characterize the galaxy cluster sample of a wide field survey it will be difficult to well recover within one sigma the cosmological parameters that mainly influence the c - M relation, using as reference a 3D c - M relation measured in cosmological N-body simulation. In this work we propose how to correct the c - M relation for projection effects and for adiabatic contraction and suggest to use these as reference for real observed data. Correcting mass and concentration estimates, as we propose, gives a measurement of the cosmological parameter within 1 - {\sigma} confidence contours.