The JADES Transient Survey II: Volumetric Supernova Rates out to z~5
Summary
This paper reports the first volumetric core-collapse (CC) and Type Ia supernova (SN Ia) rates at z sim 2–5, leveraging 83 SN candidates from the JADES Transient Survey (JTS). It confronts the challenge of photometric classification with sparse, single-epoch JWST/NIRCam data by simulating and classifying 23,000 mock SEDs across redshift, subtype, phase, luminosity, and extinction. The analysis yields consistent CC SN rates for both the full (single-SED-inclusive) and “gold” (spectroscopically/multi-epoch-confirmed) samples — 6.2^+2.2-1.7 × 10^-4 and 4.1^+1.5-1.1 × 10^-4 SNe yr^-1 Mpc^-3 in two redshift bins — and a tentative SN Ia rate of 0.3^+0.3_-0.2 × 10^-4 SNe yr^-1 Mpc^-3 at 1.92 ≤ z < 3.60.
Mathematical/empirical assessment
The classification pipeline uses STARDUST2 with modified priors, fixed x1 for single-SED fits, and strict spectral coverage constraints tied to SALT3-NIR’s rest-frame 2–20 μm range (Fig. 1). Confusion matrices (Figs. 4–5) quantify misclassification: average TPRCC ≈ 0.87 across 0.7 ≤ z ≤ 5, but TPRIa only 0.52 (spec-z) or 0.45 (photo-z), rising modestly with z (Fig. 6). The derived rates incorporate these empirically measured classification efficiencies — not analytic assumptions — and propagate asymmetric uncertainties from Poisson statistics and simulation variance. The consistency between full and gold samples suggests robustness to single-SED contamination, though the SN Ia rate remains statistically limited.
Strengths
The work sets a new observational benchmark: first high-z volumetric SN rates anchored in JWST’s unique sensitivity and resolution. Its strength lies in empirically grounding classification uncertainty — not assuming purity — via a large, physically motivated mock SED suite spanning realistic parameter grids (Table 1). The dual-sample approach (full vs. gold) transparently isolates systematic effects of photometric classification. The CC SN rates’ agreement with SFRD-based expectations — and their tentative decline beyond cosmic noon — is observationally compelling and timely.
Concerns
A genuine tension remains regarding SN Ia identification: the low TPR_Ia ( 0.4–0.5) implies substantial contamination of the CC sample by misclassified SNe Ia, especially at lower z where SALT3-NIR coverage is marginal (Fig. 1). While the paper acknowledges this, the reported SN Ia rate relies on the same uncertain classifier without independent validation at high-z — and no spectroscopic SN Ia beyond z=2.90 is included in the rate bin. Furthermore, the omission of SNe IIb ( 10% of CC SNe) and reliance on local subtype fractions may bias CC rate systematics if high-z populations differ. The “tentative decline” in CC rates is suggestive but not yet decisive given current error bars.
Final decision
Weak accept