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Published June 2016 | Submitted + Published
Journal Article Open

CLASH-VLT: Dissecting the Frontier Fields Galaxy Cluster MACS J0416.1-2403 with ∼800 Spectra of Member Galaxies

Abstract

We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields cluster MACS J0416.1-2403 (z = 0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ~600 arcmin^2, including ~800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ~2.2 r _(200) (~4 Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster (M _(200) ~ 0.9 × 10^(15) M_⊙ and σ_(V,r200) ~ 1000 km s^(−1)) presenting two major features: (i) a bimodal velocity distribution, showing two central peaks separated by ΔV _(rf) ~ 1100 km s^(−1) with comparable galaxy content and velocity dispersion, and (ii) a projected elongation of the main substructures along the NE–SW direction, with a prominent sub-clump ~600 kpc SW of the center and an isolated BCG approximately halfway between the center and the SW clump. We also detect a low-mass structure at z ~ 0.390, ~10' south of the cluster center, projected at ~3 Mpc, with a relative line-of-sight velocity of ΔV_(rf) ~ −1700 km s^(−1). The cluster mass profile that we obtain through our dynamical analysis deviates significantly from the "universal" NFW, being best fit by a Softened Isothermal Sphere model instead. The mass profile measured from the galaxy dynamics is found to be in relatively good agreement with those obtained from strong and weak lensing, as well as with that from the X-rays, despite the clearly unrelaxed nature of the cluster. Our results reveal an overall complex dynamical state of this massive cluster and support the hypothesis that the two main subclusters are being observed in a pre-collisional phase, in agreement with recent findings from radio and deep X-ray data. In this article, we also release the entire redshift catalog of 4386 sources in the field of this cluster, which includes 60 identified Chandra X-ray sources and 105 JVLA radio sources.

Additional Information

© 2016 The American Astronomical Society. Received 2015 November 8; accepted 2016 March 3; published 2016 June 8. We thank the anonymous referee for a careful reading of the manuscript and the valuable comments and suggestions provided. We acknowledge the continuous help of the ESO user support group, especially our project support astronomer, Vincenzo Mainieri, for his excellent support and advices. We acknowledge financial support from PRIN-INAF 2014 1.05.01.94.02 and from MIUR PRIN2010-2011 (J91J12000450001). I.B. acknowledges funding support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 267251 "Astronomy Fellowships in Italy" (AstroFIt). B.S. acknowledges a grant from "Consorzio per la Fisica—Trieste." P.R. acknowledges the hospitality and support of the visitor program of the DFG cluster of excellence "Origin and Structure of the Universe." G.A.O. and A.Z. are supported by NASA through Hubble Fellowship grants HST-HF2-51345.001-A and #HST-HF2-51334.001-A, respectively, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated under NASA contract NAS5-26555. J.M. is supported by the People Programme (Marie Curie Actions) of the European Union Seventh Framework Programme (FP7/2007-2013) under REA grant agreement No. 627288. This work is based on data collected at the ESO VLT (prog.ID 186.A-0798), at the NASA HST, and at the NASJ Subaru telescope. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, NAOJ (Baba et al. 2002).

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Published - apjs_224_2_33.pdf

Submitted - 1511.02522v2.pdf

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Additional details

Created:
August 22, 2023
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October 20, 2023