James Webb Space Telescope Feed Post

Paper 1: The JWST PEARLS View of the El Gordo Galaxy Cluster and of the Structure It Magnifies Published: 3/7/2023 1:50:26 AM Updated: 6/4/2023 4:58:16 AM

Paper abstract: The massive galaxy cluster El Gordo (z=0.87) imprints multitudes ofgravitationally lensed arcs onto James Webb Space Telescope (JWST)Near-Infrared Camera (NIRCam) images. Eight bands of NIRCam imaging wereobtained in the ``Prime Extragalactic Areas for Reionization and LensingScience'' (``PEARLS'') program. PSF-matched photometry across Hubble SpaceTelescope (HST) and NIRCam filters supplies new photometric redshifts. A newlight-traces-mass lens model based on 56 image multiplicities identifies thetwo mass peaks and yields a mass estimate within 500 kpc of ~(7.0 +/- 0.30) x10^14 Msun. A search for substructure in the 140 cluster members withspectroscopic redshifts confirms the two main mass components. The southeasternmass peak that contains the BCG is more tightly bound than the northwesternone. The virial mass within 1.7 Mpc is (5.1 +/- 0.60) x 10^14 Msun, lower thanthe lensing mass. A significant transverse velocity component could mean thevirial mass is underestimated. We contribute one new member to the previouslyknown z=4.32 galaxy group. Intrinsic (delensed) positions of the five securegroup members span a physical extent of ~60 kpc. Thirteen additional candidatesselected by spectroscopic/photometric constraints are small and faint with amean intrinsic luminosity ~2.2 mag fainter than L*. NIRCam imaging admits afairly wide range of brightnesses and morphologies for the group members,suggesting a more diverse galaxy population in this galaxy overdensity.