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Arxiv: Testing for Intrinsic Type Ia Supernova Luminosity Evolution at z>2 with JWST Published: 11/18/2024 9:00:01 PM Updated: 2/12/2025 5:36:52 PM

Paper abstract: The James Webb Space Telescope} (JWST) is opening new frontiers of transientdiscovery and follow-up at high-redshift. Here we present the discovery of aspectroscopically confirmed Type Ia supernova (SN Ia; SN 2023aeax) atz=2.15 with JWST, including a NIRCam multi-band light curve. SN 2023aeaxlands at the edge of traditional low-z cosmology cuts because of its bluecolor (peak rest-frame B-V~-0.3) but with a normal decline rate (\Deltam_{15}(B)~1.25), and applying a fiducial standardization with the BayeSNmodel we find the SN 2023aeax luminosity distance is in ~0.1\sigmaagreement with \LambdaCDM. SN 2023aeax is only the second spectroscopicallyconfirmed SN Ia in the dark matter-dominated Universe at z>2 (the other is SN2023adsy), giving it rare leverage to constrain any potential evolution in SNIa standardized luminosities. Similar to SN 2023adsy (B-V~0.8), SN2023aeax has a fairly extreme (but opposite) color, which may be due to thesmall sample size or a secondary factor, such as host galaxy properties.Nevertheless, the SN 2023aeax spectrum is well-represented by normal low-zSN Ia spectra and we find no definitive evolution in SN Ia standardization withredshift. Still, the first two spectroscopically confirmed z>2 SNe Ia havepeculiar colors and combine for a ~1\sigma distance slope relative to\LambdaCDM, though in agreement with recent SN Ia cosmological measurements.