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

Time series of SN H0pe imaging observations. Negative images in the three epochs are shown for each of the three images of the SN. Of the eight NIRCam filters acquired in Epoch 1 and six filters in each of Epochs 2 and 3, only three filters are depicted for clarity. The image stamps have the same orientation as in Figure 1 and are 3'' on a side. The SN appeared first in image 2a, where it was intercepted on the decline after the second IR peak in the light curve. SN 2a and SN 2b were intercepted near the first peak, and Epochs 2 and 3 also trace the second peak detected in the NIRCam LW channels of this Type Ia SN. 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.