Monthly Notices of the Royal Astronomical Society

We present an updated strong-lensing analysis of the massive cluster Abell\n370 (A370), continuing the work first presented in Lagattuta et al. (2017). In\nthis new analysis, we take advantage of the deeper imaging data from the Hubble\nSpace Telescope (HST) Frontier Fields program, as well as a large spectroscopic\nmosaic obtained with the Multi-Unit Spectroscopic Explorer (MUSE). Thanks to\nthe extended coverage of this mosaic, we probe the full 3D distribution of\ngalaxies in the field, giving us a unique picture of the extended structure of\nthe cluster and its surroundings. Our final catalog contains 584 redshifts,\nrepresenting the largest spectroscopic catalog of A370 to date. Constructing\nthe model, we measure a total mass distribution that is quantitatively similar\nto our previous work -- though to ensure a low rms error in the model fit, we\ninvoke a significantly large external shear term. Using the redshift catalog,\nwe search for other bound groups of galaxies, which may give rise to a more\nphysical interpretation of this shear. We identify three structures in narrow\nredshift ranges along the line of sight, highlighting possible infalling\nsubstructures into the main cluster halo. We also discover additional\nsubstructure candidates in low-resolution imaging at larger projected radii.\nMore spectroscopic coverage of these regions (pushing close to the A370 virial\nradius) and more extended, high-resolution imaging will be required to\ninvestigate this possibility, further advancing the analysis of these\ninteresting developments.\n

Probing 3D Structure with a Large MUSE Mosaic: Extending the Mass Model of Frontier Field Abell 370