Using Strong Gravitational Lensing to Identify Fossil Group Progenitors

Abstract

Fossil galaxy systems are classically thought to be the end result of galaxy group/cluster evolution, as galaxies experiencing dynamical friction sink to the center of the group potential and merge into a single, giant elliptical that dominates the rest of the members in both mass and luminosity. Most fossil systems discovered lie within $z<0.2$, which leads to the question: what were these systems' progenitors? Such progenitors are expected to have imminent or ongoing major merging near the brightest group galaxy (BGG) that, when concluded, will meet the fossil criteria within the look back time. Since strong gravitational lensing preferentially selects groups merging along the line of sight, or systems with a high mass concentration like fossil systems, we searched the CASSOWARY survey of strong lensing events with the goal of determining if lensing systems have any predisposition to being fossil systems or progenitors. We find that $\sim$13% of lensing groups are identified as traditional fossils while only $\sim$3% of non-lensing control groups are. We also find that $\sim$23% of lensing systems are traditional fossil progenitors compared to $\sim$17% for the control sample. Our findings show that strong lensing systems are more likely to be fossil/pre-fossil systems than comparable non-lensing systems. Cumulative galaxy luminosity functions of the lensing and non-lensing groups also indicate a possible, fundamental difference between strong lensing and non-lensing systems' galaxy populations with lensing systems housing a greater number of bright galaxies even in the outskirts of groups.

14 pages, 6 figures, 2 tables, submitted to ApJ

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Cited by in corpus (7)

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• RELICS: ICL Analysis of the $z=0.566$ merging cluster WHL J013719.8-08284
• Reconstructing the extended structure of multiple sources strongly lensed by the ultra-massive elliptical galaxy SDSS J0100+1818
• Cosmography from accurate mass modeling of the lens group SDSS J0100+1818: five sources at three different redshifts
• Chandra and HST Snapshots of Fossil System Progenitors
• Independent Evidence for earlier formation epochs of fossil groups of galaxies through the intracluster light: the case for RX J100742.53+380046.6
• The lens SW05 J143454.4+522850: a fossil group at redshift 0.6?