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

NIRSpec spectra of Arc 1a (=Arc NS 969, top) and a nearby object (Arc NS 46, bottom). Wavelengths are in the observed frame, and the spectra are in F? in units of 10-19 erg s-1 cm-2 °A -1 . The G140M spectrum is plotted in green and the G235M spectrum in blue. Detected lines are marked. The images to the right of each panel show the respective source with MSA slit positions overlaid, and are oriented the same as in Figure 1. Colors follow the prescription in Trilogy (Coe et al. 2012) with red showing F200W, green showing F150W, and blue showing F090W. The objects were observed in the same triplet of MSA slits with Arc 1a in the easternmost segment and Arc NS 46 in the middle segment, neither perfectly centered in the respective segments. The blue outline in each image shows the microshutter from which the spectrum to its left was extracted. 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.