James Webb Space Telescope Feed Post

The JWST Discovery of the Triply-imaged Type Ia "Supernova H0pe" and Observations of the Galaxy Cluster PLCK G165.7+67.0 Published: 9/14/2023 12:40:01 AM Updated: 9/14/2023 12:40:01 AM

Paper abstract: A Type Ia supernova (SN) at z=1.78 was discovered in James Webb SpaceTelescope Near Infrared Camera imaging of the galaxy cluster PLCK G165.7+67.0(G165; z = 0.35). The SN is situated 1.5-2kpc from its host galaxy Arc 2 andappears in three different locations as a result of gravitational lensing byG165. These data can yield a value for Hubble's constant using time delays fromthis multiply-imaged SN Ia that we call "SN H0pe." Over the entire field weidentified 21 image multiplicities, confirmed five of them using Near-InfraredSpectrograph (NIRspec), and constructed a new lens model that gives a totalmass within 600kpc of (2.6 \pm 0.3) \times 10^{14} M_{\odot}. Thephotometry uncovered a galaxy overdensity at Arc 2's redshift. NIRSpecconfirmed six member galaxies, four of which surround Arc 2 with relativevelocity <~900 km s^{-1} and projected physical extent <~33kpc. Arc 2 dominates the stellar mass ((5.0 \pm 0.1) \times 10^{11}M_{\odot}), which is a factor of ten higher than other members of thiscompact galaxy group. These other group members have specific star formationrates (sSFR) of 2-260Gyr^{-1} derived from the H\alpha-line flux correctedfor stellar absorption, dust extinction, and slit losses. Another groupcentered on the dusty star forming galaxy Arc 1 is at z=2.24. The total SFRfor the Arc 1 group (gtrsim M_{\odot} yr^{-1}) translates to a supernovarate of ~1 SNe yr^{-1}, suggesting that regular monitoring of thiscluster may yield additional SNe.