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

TL;DR

This study measures the average mass density profiles of galaxy clusters using magnification bias of submillimetre galaxies, revealing scale-dependent profiles and concentration variations, and highlighting a transition region between cluster and galactic halos.

Contribution

It introduces a method to derive detailed mass density profiles across scales using magnification bias, revealing non-uniform profiles and a transition feature not previously discussed.

Findings

Mass estimates increase with scale from 5.8 to 51.5×10^{13} M_0

Concentration parameters vary from 0.74 to 1.74 across scales

A systematic lack of signal at the cluster-galaxy halo transition was observed.

Abstract

In this work we want to study the average mass density profile of tens to hundreds of clusters of galaxies acting as lenses that produce a magnification bias on the SMGs, and to estimate their associated masses and concentrations for different richness ranges. The background sample is composed of SMGs observed by Herschel with 1.2<z<4.0 (mean redshift at ~2.3) while the foreground sample is made up of galaxy clusters extracted from the SDSS III with photometric redshifts of 0.05< z< 0.8 (mean redshift at ~0.38). Measurements are obtained by stacking the SMG--cluster pairs to estimate the cross-correlation function using the Davis-Peebles estimator. This methodology allows us to derive the mass density profile for a wide range of angular scales, ~2-250 arcsec or ~10-1300 kpc for z=0.38, with a high radial resolution. We find that It is impossible to fit the data with a single mass density profile at all scales. As for the outer part, the estimated average masses increase from $M_{200c}=5.8$ to $51.5\times 10^{13} M_\odot$ and the concentration parameter from C=0.74 to 1.74. In the small-scale regions, the obtained average masses fluctuate around $M_{200c}=3-4 \times 10^{13}M_\odot$ with average C~4. The total average masses are in perfect agreement with the M-R relationship estimated from the cluster catalogue. While the estimated average C values of the central galactic halos are in agreement with traditional M-C relationships, we find low concentrations for the outer part. Moreover, C decrease for lower R values, probably indicating that the group of galaxies cannot be considered to be relaxed systems. Finally, we notice a systematic lack of signal at the transition between the dominance of the cluster halo and the central galactic halo (~100 kpc). This feature is also present in previous studies using different catalogues and/or methodologies, but is never discussed.