Spectroscopy of the supernova H0pe host galaxy at redshift 1.78

Supernova (SN) H0pe was discovered as a new transient in James Webb Space Telescope (JWST) NIRCam images of the galaxy cluster PLCK G165.7 +67.0 taken as part of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) JWST GTO program (ID 1176) on 2023 March 30. The transient is a compact source associated with a background galaxy that is stretched and triply imaged by the strong gravitational lensing of the cluster. This paper reports spectra in the 950-1370 nm observer frame of two of the galaxy images obtained with Large Binocular Telescope (LBT) Utility Camera in the Infrared (LUCI) in long-slit mode two weeks after the JWST observations. The individual and average spectra show the [O ii] lambda lambda 3727,3730 doublet and the Balmer and 4000A breaks at redshift z = 1:783 +/- 0:002. The code investigating galaxy emission (CIGALE) best-fit model of the spectral energy distribution indicates that the host galaxy of SN H0pe is massive (M-star similar or equal to 6 x10(10) M-circle dot after correcting for a magnification factor mu similar to 7) with a predominantly intermediate-age (similar to 2 Gyr) stellar population, moderate extinction, and a magnification-corrected star formation rate similar or equal to 13 M-circle dot yr(-1), consistent with being below the main sequence of star formation. These properties suggest that H0pe might be a type Ia SN. Additional observations of SN H0pe and its host recently carried out with JWST (JWST-DD-4446; PI: B. Frye) will be able to both determine the SN classification and confirm its association with the galaxy analyzed in this work.

Automated summary

Supernova (SN) H0pe was discovered as a new transient in James Webb Space Telescope (JWST) NIRCam images of the galaxy cluster PLCK G165.7 +67.0. The transient is a compact source associated with a background galaxy that is stretched and triply imaged by the strong gravitational lensing of the cluster. Spectra obtained two weeks after the JWST observations show the [O ii] lambda lambda 3727,3730 doublet and the Balmer and 4000A breaks at redshift z = 1:783 +/- 0:002, indicating that SN H0pe might be a type Ia SN. Further observations with JWST will confirm its association with the analyzed galaxy and determine its classification.