Strong Gravitational Lensing by the Super-massive cD Galaxy in Abell 3827

TL;DR

This paper reports the discovery and analysis of strong gravitational lensing features in the core of Abell 3827, revealing a highly-magnified ring and a secondary arc, and estimating the cluster's mass.

Contribution

First detailed gravitational lensing analysis of Abell 3827's core, revealing a massive BCG and providing mass estimates exceeding X-ray derived values.

Findings

Mass within 37 h^-1 kpc is (2.7 +- 0.4) x 10^13 Msun

Lensing mass exceeds X-ray estimates by an order of magnitude

The BCG may be the most massive galaxy nearby

Abstract

We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly-magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z~0.2. Located ~20" away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z~0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the BCG and other galaxies. We derive a total mass of (2.7 +- 0.4) x 10^13 Msun within 37 h^-1 kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby Universe.