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

The z = 1.65 galaxy group. Photometric redshifts identified a group of seven galaxies within 15'' ± 20'' in the G165 NIRCam parallel field. These galaxies broadly share similar colors and morphology, and photometric SED fitting finds all but one (yellow arrow) to be quiescent. These galaxies have a total physical extent of ?130 kpc, making them another potential compact galaxy group. 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.