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Arxiv: Discovery of An Apparent Red, High-Velocity Type Ia Supernova at z = 2.9 with JWST Published: 6/7/2024 8:03:04 PM Updated: 6/10/2024 7:44:22 PM

Paper abstract: We present the JWST discovery of SN 2023adsy, a transient object located in ahost galaxy JADES-GS+53.13485-27.82088 with a host spectroscopic redshiftof 2.903\pm0.007. The transient was identified in deep James Webb SpaceTelescope (JWST)/NIRCam imaging from the JWST Advanced Deep ExtragalacticSurvey (JADES) program. Photometric and spectroscopic followup with NIRCam andNIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIRcolor, and spectroscopic information all consistent with a Type Iaclassification. Despite its classification as a likely SN Ia, SN 2023adsy isboth fairly red (E(B-V)~0.9) despite a host galaxy with low-extinction andhas a high Ca II velocity (19,000\pm2,000km/s) compared to the generalpopulation of SNe Ia. While these characteristics are consistent with someCa-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighterthan the low-z Ca-rich population. Although such an object is too red for anylow-z cosmological sample, we apply a fiducial standardization approach to SN2023adsy and find that the SN 2023adsy luminosity distance measurement is inexcellent agreement (<~1\sigma) with \LambdaCDM. Therefore unlikelow-z Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indicationthat SN Ia standardized luminosities change significantly with redshift. Alarger sample of distant SNe Ia is required to determine if SN Ia populationcharacteristics at high-z truly diverge from their low-z counterparts, and toconfirm that standardized luminosities nevertheless remain constant withredshift.