Imaging the Thermal and Kinematic Sunyaev–Zel'dovich Effect Signals in a Sample of 10 Massive Galaxy Clusters: Constraints on Internal Velocity Structures and Bulk Velocities

Abstract

We have imaged the Sunyaev–Zel'dovich (SZ) effect signals at 140 and 270 GHz toward 10 galaxy clusters with Bolocam and AzTEC/ASTE. We also used Planck data to constrain the signal at large angular scales, Herschel–SPIRE images to subtract the brightest galaxies that comprise the cosmic infrared background (CIB), Chandra imaging to map the electron temperature Tₑ of the intra-cluster medium, and Hubble Space Telescope imaging to derive models of each galaxy cluster's mass density. The galaxy clusters gravitationally lens the background CIB, which produced an on-average reduction in brightness toward the galaxy clusters' centers after the brightest galaxies were subtracted. We corrected for this deficit, which was between 5% and 25% of the 270 GHz SZ effect signal within R₂₅₀₀. Using the SZ effect measurements, along with the X-ray constraint on Tₑ, we measured each galaxy cluster's average line of sight (LOS) velocity v_z within R₂₅₀₀, with a median per-cluster uncertainty of ±700 km s⁻¹. We found an ensemble-mean ⟨v_z⟩ of 430 ± 210 km s⁻¹, and an intrinsic cluster-to-cluster scatter σᵢₙₜ of 470 ± 340 km s⁻¹. We also obtained maps of v_z over each galaxy cluster's face with an angular resolution of 70''. All four galaxy clusters previously identified as having a merger oriented along the LOS showed an excess variance in these maps at a significance of ≃2–4σ, indicating an internal v_z rms of ≳1000 km s⁻¹. None of the six galaxy clusters previously identified as relaxed or plane-of-sky mergers showed any such excess variance.

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