Abstract
We present an analysis of MUSE observations obtained on the massive Frontier Fields cluster Abell 2744. This new dataset covers the entire multiply-imaged region around the cluster core. We measure spectroscopic redshifts for HST-selected continuum sources together with line emitters blindly detected in the datacube. The combined catalog consists of 514 spectroscopic redshifts (with 414 new identifications), including 156 cluster members and 326 magnified background sources. We use this redshift information to perform a strong-lensing analysis of all multiple images previously found in the deep Frontier Field images, and add three new MUSE-detected multiply-imaged systems with no obvious HST counterpart. The combined strong lensing constraints include a total of 60 systems producing 188 images altogether, out of which 29 systems and 83 images are spectroscopically confirmed, making Abell 2744 one of the most well-constrained clusters to date. A parametric mass model including two cluster-scale components in the core and several group-scale substructures at larger radii accurately reproduces all the spectroscopic multiple systems, reaching an rms of 0.67" in the image plane. Overall, the large number of spectroscopic redshifts gives us a robust model and we estimate the systematics on the mass density and magnification within the cluster core to be typically ~9%.
Highlights
Cluster of galaxies represent a natural merging process over large scales, and as such gather many valuable observables for our Universe
We start with a parametrisation similar to Jauzac et al (2015), namely: two dark matter clumps representing cluster-scale potentials and two smallscale background galaxies (MUSE9778 and MUSE7257), in addition to identified cluster members (246)
Thanks to the 18.5 hours of Multi Unit Spectroscopic Explorer (MUSE) coverage we perform spectroscopic analysis and construct a redshift catalog of a total of 514 objects, including 156 cluster members matching in velocity the large radii structure found by Owers et al (2011)
Summary
Cluster of galaxies represent a natural merging process over large scales, and as such gather many valuable observables for our Universe. From a statistical point of view they can constraint various physical processes, such as structure formation or cosmological parameters (Schwinn et al 2016; Jullo et al 2010). By measuring cluster mass distributions we gain insight into cluster-specific properties, such as dark matter content (Bradac et al 2008, Umetsu et al 2009). Strong gravitational lensing precisely measures the enclosed mass of a cluster at a given radius, making it a powerful tool for studying dark and luminous matter. The effect occurs when the curvature of spacetime is large enough near the cluster centre to make different light paths from the same source converge on the field of view of the observer
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