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An extreme case of galaxy and cluster co-evolution at z = 0.7

Abstract : We report the discovery of eMACS J0252.4-2100 (eMACS J0252), a massive and highly evolved galaxy cluster at z = 0.703. Our analysis of Hubble Space Telescope imaging and VLT/MUSE and Keck/DEIMOS spectroscopy of the system finds a high-velocity dispersion of 1020$^{+180}_{-190}$ km s-1 and a high (if tentative) X-ray luminosity of (1.2 ± 0.4) × 1045 erg s-1 (0.1-2.4 keV). As extreme is the system's brightest cluster galaxy, a giant cD galaxy that forms stars at a rate of between 85 and 300 M yr-1 and features an extended halo of diffuse [O II] emission, as well as evidence of dust. Its most remarkable properties, however, are an exceptionally high ellipticity and a radially symmetric flow of gas in the surrounding intracluster medium, potential direct kinematic evidence of a cooling flow. A strong-lensing analysis, anchored by two multiple-image systems with spectroscopic redshifts, finds the best lens model to consist of a single cluster-scale halo with a total mass of (1.9 ± 0.1) × 1014 M within 250 kpc of the cluster core and, again, an extraordinarily high ellipticity of e = 0.8. Although further, in-depth studies across the electromagnetic spectrum (especially in the X-ray regime) are needed to conclusively determine the dynamical state of the system, the properties established so far suggest that eMACS J0252 must have already been highly evolved well before z ~ 1, making it a prime target to constrain the physical mechanisms and history of the co-evolution or dark-matter haloes and baryons in the era of cluster formation.
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Submitted on : Friday, July 1, 2022 - 1:55:55 PM
Last modification on : Saturday, July 2, 2022 - 3:40:14 AM

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H. Ebeling, J. Richard, I. Smail, A. C. Edge, A. M. Koekemoer, et al.. An extreme case of galaxy and cluster co-evolution at z = 0.7. Monthly Notices of the Royal Astronomical Society, 2021, 508, pp.3663-3671. ⟨10.1093/mnras/stab2725⟩. ⟨insu-03711483⟩

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