Compact Groups analysis using weak gravitational lensing II: CFHT Stripe 82 data

TL;DR

This study uses weak gravitational lensing to analyze the mass distribution of Compact Groups in the CFHT Stripe 82 data, revealing dependencies on surface brightness and concentration, and comparing lensing with dynamical estimates.

Contribution

It provides the first detailed lensing analysis of Compact Groups using CFHT data, highlighting the influence of surface brightness and concentration on the lensing signal and validating lensing mass estimates against dynamical methods.

Findings

Higher surface brightness CGs show stronger lensing signals.

Most concentrated CGs exhibit significant lensing consistent with isothermal and NFW profiles.

Lensing results agree with dynamical estimates for less contaminated, high-brightness groups.

Abstract

In this work we present a lensing study of Compact Groups (CGs) using data obtained from the high quality Canada-France-Hawaii Telescope Stripe 82 Survey. Using stacking techniques we obtain the average density contrast profile. We analyse the lensing signal dependence on the groups surface brightness and morphological content, for CGs in the redshift range $z = 0.2 - 0.4$. We obtain a larger lensing signal for CGs with higher surface brightness, probably due to their lower contamination by interlopers. Also, we find a strong dependence of the lensing signal on the group concentration parameter, with the most concentrated quintile showing a significant lensing signal, consistent with an isothermal sphere with $\sigma_V =336 \pm 28$ km/s and a NFW profile with $R_{200}=0.60\pm0.05$ $h_{70}^{-1}$Mpc. We also compare lensing results with dynamical estimates finding a good agreement with lensing determinations for CGs with higher surface brightness and higher concentration indexes. On the other hand, CGs that are more contaminated by interlopers show larger dynamical dispersions, since interlopers bias dynamical estimates to larger values, although the lensing signal is weakened.