The First Weak-lensing Analysis with the James Webb Space Telescope: SMACS J0723.3–7327

Abstract

Utilizing the James Webb Space Telescope Early Release NIRCam Observations, we perform a weak-lensing analysis of the massive galaxy cluster SMACS J0723.3–7327 ( z = 0.39). We investigate the spatial variation of the point-spread function (PSF) from the stars in the mosaic image. Our measurements show that the PSF for both modules has very small spatial and temporal variation with average complex ellipticity components of e _1 = 0.007 ± 0.001 and e _2 = 0.029 ± 0.001 in the observed north-up reference frame. We create PSF models through a principal component analysis of the stars and show that they properly account for the ellipticity of the PSF with residual shapes of e _1 = (0.3 ± 3.5) × 10 ^−4 and e _2 = (1.8 ± 4.0) × 10 ^−4 . We select background galaxies by their photometric redshift and measure galaxy shapes by model fitting. Our weak-lensing source catalog achieves ∼215 galaxies arcmin ^−2 . We map the convergence field of SMACSJ0723 and detect the cluster with a peak significance of 12.2 σ . The mass distribution is found to elongate in the east–west direction with an extension to the northeast edge of the field of view where a candidate substructure is found in the Chandra X-ray imaging. We fit the tangential shear with a Navarro–Frenk–White model and estimate the mass of the cluster to be M _500 = 7.9 ± 1.1 × 10 ^14 M _⊙ ( M _200 = 11.4 ± 1.5 × 10 ^14 M _⊙ ), which agrees with existing mass estimates. Combining the multiwavelength evidence from literature with our weak-lensing analysis, we hypothesize that SMACSJ0723 is observed near first pericenter passage and we identify candidate radio relics.

Keywords

• Weak gravitational lensing
• James Webb Space Telescope
• Galaxy clusters
• Hubble Space Telescope