James Webb Space Telescope Feed Post


EarlyReleases
Date: 9/15/2023

The JWST Discovery of the Triply-imaged Type Ia "Supernova H0pe" and Observations of the Galaxy Cluster PLCK G165.7+67.0


NIRCam color image of the central region of G165. G165 is a double cluster with prominent NE and SW components. Colors follow the prescription in Trilogy (Coe et al. 2012) with red showing F444W and F356W, green showing F277W and F200W, and blue showing F150W and F090W. The 21 image systems used in our lens model are marked. They include the DSFG as Arcs 1a and 1b/c. The triply-imaged SN is labeled as “SN 2a/2b/2c.” The orientation and image scale are provided for reference. Abstract: A Type Ia supernova (SN) at z=1.78 was discovered in James Webb Space Telescope 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 and appears in three different locations as a result of gravitational lensing by G165. These data can yield a value for Hubble's constant using time delays from this multiply-imaged SN Ia that we call "SN H0pe." Over the entire field we identified 21 image multiplicities, confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new lens model that gives a total mass within 600kpc of (2.6±0.3)×1014 M?. The photometry uncovered a galaxy overdensity at Arc 2's redshift. NIRSpec confirmed six member galaxies, four of which surround Arc 2 with relative velocity ?900 km s-1 and projected physical extent ?33 kpc. Arc 2 dominates the stellar mass ((5.0±0.1)×1011 M?), which is a factor of ten higher than other members of this compact galaxy group. These other group members have specific star formation rates (sSFR) of 2-260Gyr-1 derived from the Ha-line flux corrected for stellar absorption, dust extinction, and slit losses. Another group centered on the dusty star forming galaxy Arc 1 is at z=2.24. The total SFR for the Arc 1 group (gtrsim M? yr-1) translates to a supernova rate of ~1 SNe yr-1, suggesting that regular monitoring of this cluster may yield additional SNe.