We present an updated strong lensing model of the galaxy cluster MACS J0416.1-2403 with the largest sample of multiple images with spectroscopic redshifts in a galaxy cluster field to date. Furthermore, we demonstrate the effectiveness of JWST particularly its NIRISS camera, for strong lensing studies. We use the JWST 's NIRCam imaging and NIRSpec and NIRISS spectroscopy from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). The cluster mass model is constrained using Lenstool software. Our new dataset, used for constraining the lens model, comprises 303 secure multiple images from 111 background sources and includes systems with previously known MUSE redshift and systems for which we obtained spectroscopic redshift for the first time using NIRISS and NIRSpec spectroscopy. The total number of secure spectroscopic systems is >20% higher than in the previous strong lensing studies of this cluster. The derived strong lensing model can reproduce multiple images with the root-mean-square distance of 0.53''. We also provide a full catalogue with 415 multiple images, including less reliable candidates. We furthermore demonstrate the effectiveness of JWST particularly NIRISS, for strong lensing studies. As NIRISS F115W, F150W, and F200W grism spectroscopy captures at least two of the [OII] 3727, [OIII] 4959, 5007, and Ha lines at 1 < z < 3 (a redshift range particularly relevant for strong lensing studies) without target pre-selection, it complements MUSE and NIRSpec observations extremely well.

• Paper
• Lens model (catalogs, lenstool parameter files, maps)

We report an updated mass and magnification model of galaxy cluster Abell 370 using new NIRCam and NIRISS data from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using Lenstool and a combination of archival HST and MUSE data with new JWST data as constraints, we derive an improved gravitational lensing model and extract magnifications of background galaxies with uncertainties. Using our best fit model, we perform a search for new multiply imaged systems via predicted positions. We report no new multiply imaged systems with identifiable redshifts, likely due to already very deep HST and Spitzer data, but confirm a z∼8 multiply imaged system by measuring its redshift with NIRISS and NIRSpec spectra. We find that the overall shape of the critical curve for a source at z=9.0 is similar to previous models of Abell 370, with small changes. We investigate the z∼8 galaxy with two images observable with an apparent magnitude in the F125W band of 26.0±0.2 and 25.6±0.1. After correcting for the magnifications of the images, 7.2+0.2−1.2 and 8.7+0.4−0.4, we use SED fitting to find an intrinsic stellar mass of log(M∗/M⊙) = 7.35+0.04−0.05, intrinsic SFR of 3.5+2.2−1.4 M⊙/yr, and MUV of -21.3+0.2−0.2, which is close to the knee of the luminosity function at that redshift. Our model, and corresponding magnification, shear, and convergence maps are available on request and will be made publicly available on MAST in a CANUCS data release (DOI: 10.17909/ph4n-6n76).

• Paper
• Lens model (catalogs, lenstool parameter files, maps)