Multiwavelength Analysis of the Merging Galaxy Cluster A115

April 2019 • 2019ApJ...874..143K

Authors • Kim, Mincheol • Jee, M. James • Finner, Kyle • Golovich, Nathan • Wittman, David M. • van Weeren, R. J. • Dawson, W. A.

Abstract • A115 is a merging galaxy cluster at z ∼ 0.2 with a number of remarkable features, including a giant (∼2.5 Mpc) radio relic, two asymmetric X-ray peaks with trailing tails, and a peculiar line-of-sight velocity structure. We present a multiwavelength study of A115 using optical imaging data from Subaru, X-ray data from Chandra, and spectroscopic data from the Keck/DEIMOS and MMT/Hectospec instruments. Our weak-lensing (WL) analysis shows that the cluster is composed of two subclusters whose mass centroids are in excellent agreement with the two brightest cluster galaxy positions (≲10″). By modeling A115 with a superposition of two Navarro-Frenk-White halos, we determine the masses of the northern and southern subclusters to be {M}₂₀₀={1.58}_-0.49^+0.56× {10}¹⁴ {M}_⊙ and {3.15}_-0.71^+0.79× {10}¹⁴ {M}_⊙, respectively. Combining the two halos, we estimate the total cluster mass to be {M}₂₀₀={6.41}_-1.04^+1.08× {10}¹⁴ {M}_⊙ at {R}₂₀₀={1.67}_-0.09^+0.10 Mpc. These WL masses are significantly (a factor of 3-10) lower than what is implied by the X-ray and optical spectroscopic data. We attribute the difference to the gravitational and hydrodynamic disruption caused by the collision between the two subclusters.

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Kyle Finner

Postdoctoral Research Associate