Lensing Model of MACS J1149.5+2223 - I. Cluster mass reconstruction

Measurements of the total logarithmic central slope of the mass profile in galaxy clusters constrain their evolution and assembly history and that of their brightest cluster galaxies. We report the first full surface brightness distribution modelling of the inner region of the galaxy cluster MACS J1149.5+2223. We compare these results with a position-based modelling approach for which we employ more than twice the previously known positional constraints. This is the first time that the detailed lensed image configuration of two non-central cluster galaxies with Einstein rings has been mapped. Due to the extended radial coverage provided by the multiple images in this system, we are able to determine the slope $\partial \log{ κ}/\partial \log{R} = -0.33$ of the total projected mass distribution from $8$ to $80~\mathrm{kpc}$. This is within the cluster-to-cluster scatter estimates from previous cluster measurements. Our reconstruction of the image surface brightness distribution of the large central spiral galaxy has a root mean square residual for all image pixels of $1.14~σ$, where $σ$ is the observational background noise. This corresponds to a reconstruction of the positions of bright clumps in the central galaxy with an rms of $0.063~\mathrm{arcsec}$.

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