The Pantheon+ Analysis: The Full Dataset and Light-Curve Release (2112.03863v2)

Abstract: Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ($z$). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with $z<0.01$ such that SN systematic covariance can be included in a joint measurement of the Hubble constant (H$_0$) and the dark energy equation-of-state parameter ($w$). We use the large sample to compare properties of 151 SNe Ia observed by multiple surveys and 12 pairs/triplets of "SN siblings" - SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al. (2022b), and the determination of H$_0$ is discussed by Riess et al. (2022). These analyses will measure w with $\sim3\%$ precision and H$_0$ with 1 km/s/Mpc precision.

• The paper introduces the expanded Pantheon+ dataset featuring 1550 unique Type Ia supernovae to enhance cosmological parameter estimation.
• It employs advanced calibration techniques and refined redshift corrections, ensuring higher accuracy in light curve measurements.
• The dataset’s extended redshift range and analysis of sibling supernovae reduce uncertainties, supporting more precise H0 and dark energy evaluations.

Analysis of the Pantheon+ Dataset and Its Implications for Supernova Cosmology

The paper "The Pantheon+ Analysis: The Full Dataset and Light-Curve Release" presents a comprehensive compilation and analysis of spectroscopically confirmed Type Ia supernovae (SNe Ia), which serve as crucial observables for inferring cosmological parameters. This extensive dataset, referred to as Pantheon+, includes 1701 light curves of 1550 unique supernovae, a substantial increase from previous compilations like the initial Pantheon dataset, which included 1048 SNe. This enrichment is largely due to the inclusion of data from 18 different surveys, enhancing both the depth and breadth of the analysis by incorporating a wide range of redshifts.

Key Contributions

1. Expanded Dataset and Enhanced Calibration: The Pantheon+ dataset encompasses a diverse set of observations across multiple surveys, extending the redshift range and increasing low-redshift coverage. This expansion improves the sample's statistical power and facilitates a more robust determination of cosmological parameters such as the Hubble constant (H₀) and the equation-of-state parameter of dark energy (w).
2. Improved Redshift and Peculiar Velocity Measurements: A meticulous reevaluation of redshift data and peculiar velocity corrections ensures a higher accuracy in distance measurements, essential for precise cosmological inference. This refinement is critical in resolving tensions in H₀ measurements and understanding cosmic expansion dynamics.
3. Cross-calibration and Recalibration Efforts: Integration of new calibration techniques enhances the consistency across varied datasets. The application of these recalibrations addresses systematic discrepancies and supports a more reliable use of SNe Ia as standard candles.
4. Systematic Error Analysis and Covariance Treatment: The authors employ stringent light-curve selection criteria and introduce a systematic covariance matrix to account for potential data dependencies. This approach allows for more accurate error propagation in cosmological analyses, reinforcing the statistical soundness of the inferred parameters.
5. Sibling and Duplicate Supernova Studies: By analyzing "sibling supernovae" (multiple SNe within the same galaxy) and "duplicate supernovae" (SNe observed by different surveys), the paper assesses the consistency of supernova properties and addresses potential systematic biases in distance estimation.

Implications for Cosmological Measurements

The Pantheon+ analysis facilitates precise measurements of w and H₀, targeting an uncertainty of ~3% for w and ~1 km/s/Mpc for H₀. Such precision is pivotal for understanding the nature of dark energy and for refining the cosmic distance ladder. The robust dataset enhances the potential for systematic error mitigation, a crucial aspect as future surveys like LSST and Roman Space Telescope aim to explore cosmological phenomena with unprecedented precision.

Future Directions and Impact

The implications of Pantheon+ extend beyond immediate cosmological applications. As the dataset informs our understanding of dark energy and the expansion of the universe, it sets a foundation for future observational campaigns to build upon. The methodologies and calibration protocols established here will serve as benchmarks for upcoming surveys, ensuring the reliability of supernovae as cosmological tools.

In conclusion, the Pantheon+ dataset marks a significant milestone in supernova cosmology, offering a high-fidelity resource for the community. Its contributions to refining cosmological constants and addressing existing discrepancies hold profound ramifications for our comprehension of the universe's accelerating expansion and the fundamental properties of dark energy.