Spectroscopic and X-ray Modeling of the Strong Lensing Galaxy Cluster MACS J0138.0-2155

Abstract

We model the total mass and galactic substructure in the strong lensing galaxy cluster MACS J0138.0-2155 using a combination of Chandra X-ray data, Multi-Unit Spectroscopic Explorer (MUSE) spectroscopy, and Hubble Space Telescope imaging. MACS J0138.0-2155 lenses a source galaxy at $z=1.95$ which hosts two strongly lensed supernovae, Requiem and Encore. We find MACS J0138.0-2155 to have an X-ray temperature of $6.7\pm 0.4$ keV and a velocity dispersion of cluster member galaxies of $718_{-182}^{+132}$ km s${}^{-1}$. These lead to the mass estimates for the cluster of $M_{500}=5.2_{-1.2}^{+1.5}\times 10^{14}{M}_{\odot }$ from the X-ray results and $M_{200}\approx 3.6_{-2.7}^{+2.0}\times 10^{14}{M}_{\odot }$ from the velocity dispersion results. The round morphology of the X-ray emission indicates that this cluster is relaxed with an ellipticity within the lensing region of $e=0.12\pm 0.03$. Using 18 of the brightest, non-blended, quiescent galaxies, we fit the cluster specific Faber-Jackson relation, including a set of 81 variations in the analysis choices to estimate the systematic uncertainties in our results. We find a slope of $\alpha =0.26\pm 0.06(stat.)\pm 0.03(sys.)$ with an intrinsic scatter of $\Delta \sigma =31_{-6}^{+8}(stat.)\pm 4(sys.)$ km s${}^{-1}$ at a reference velocity dispersion of $\sim 220$ km s${}^{-1}$. We also report on significant galaxies along the line-of-sight potentially impacting the lens modeling, including a massive galaxy with stellar velocity dispersion of $236\pm 3$ km s${}^{-1}$ which lies close in projection to the central cluster galaxy. This galaxy is part of a small group at a slightly higher redshift than the cluster.

accepted to Open Journal of Astrophysics