First Cosmological Results using Type Ia Supernovae from the Dark Energy Survey: Measurement of the Hubble Constant (1811.02376v2)

Abstract: We present an improved measurement of the Hubble constant (H_0) using the 'inverse distance ladder' method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018 < z < 0.85 to existing distance measurements of 122 low redshift (z < 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H_0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H_0 = 67.8 +/- 1.3 km s-1 Mpc-1 (statistical and systematic uncertainties, 68% confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H_0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a LCDM universe (Planck Collaboration et al. 2018).

• The paper uses the inverse distance ladder method with DES Type Ia supernovae and BAO data to measure H₀ at 67.8 km s⁻¹ Mpc⁻¹.
• It applies a blinded data approach and carefully assesses systematic uncertainties to bolster the reliability of its cosmological parameter estimation.
• The results align with CMB predictions under the ΛCDM model, contributing to the debate on local and early universe measurements of the Hubble Constant.

Measurement of the Hubble Constant Using Type Ia Supernovae from the Dark Energy Survey

This paper presents a meticulous analysis of the Hubble constant ($H_0$) derived using Type Ia supernovae (SNe Ia) observed in the Dark Energy Survey (DES). By employing the inverse distance ladder method, this research combines data from 207 SNe Ia from DES at redshifts ranging from $0.018 < z < 0.85$ with existing low-redshift ($z < 0.07$) SNe Ia and Baryon Acoustic Oscillations (BAOs). Such a methodology stands in contrast to the traditional distance ladder method, which relies on parallax and Cepheid variable stars for calibration. Instead, the inverse distance ladder method aligns the intrinsic magnitude of SNe Ia using absolute distance measurements provided by the BAOs, calibrated at different redshift ranges, offering a robust framework to measure $H_0$ with minimal assumptions on the cosmological model.

The paper reports a value of $H_0 = 67.8$ km s$^{-1}$ Mpc$^{-1}$ with an estimated statistical and systematic uncertainty within a 68% confidence interval. The results agree well with those predicted by the Cosmic Microwave Background (CMB) assuming a $\Lambda$CDM universe, specifically referencing the works of Planck 2018 which postulate $H_0 = 67.4 \pm 0.5$ km s$^{-1}$ Mpc$^{-1}$. Notably, the analysis employs a blinded data approach to mitigate confirmation bias, thereby ensuring the objectivity and reliability of the derived results.

Significant attention is directed toward the systematic uncertainties potentially affecting the measurement, encompassing calibration errors, empirical model parameters, and population biases within the SNe Ia survey. The rigorous assessment indicates that the systematic uncertainties are generally smaller than their statistical counterparts, reinforcing the robustness of the findings. However, the paper also recognizes the need for continued vigilance in identifying and quantifying these uncertainties to further refine $H_0$ estimations.

The implications of this work are multifaceted. Firstly, it contributes substantively to the ongoing discourse regarding the discrepancy often observed between local measurements of $H_0$ and those inferred from the early universe indicators such as the CMB. The tension highlighted between the local distance ladder results and those from Planck suggests avenues for exploring potential new physics beyond the standard cosmological model, such as modifications to the standard $\Lambda$CDM framework or other exotic factors, including dark radiation or variations in the relativistic species.

Looking forward, the research underscores the utility of the inverse distance ladder methodology as a complementary approach to traditional techniques, offering a more model-independent avenue for cosmological parameter estimation. By integrating data from such rich and varied sources as the DES, this approach may serve as a template for future efforts utilizing upcoming survey results, such as those from DESI and Euclid, to further constrain $H_0$ and probe the underlying physics of our universe.

This paper exemplifies the careful integration of observational data across various cosmic distances and redshifts, contributing a crucial piece to the puzzle of our expanding universe and stimulating further investigation into any underlying tensions in the fabric of cosmological measurements.