The Dark Energy Survey Supernova Program: An updated measurement of the Hubble constant using the Inverse Distance Ladder (2406.05049v1)

Abstract: We measure the current expansion rate of the Universe, Hubble's constant $H_0$, by calibrating the absolute magnitudes of supernovae to distances measured by Baryon Acoustic Oscillations. This `inverse distance ladder' technique provides an alternative to calibrating supernovae using nearby absolute distance measurements, replacing the calibration with a high-redshift anchor. We use the recent release of 1829 supernovae from the Dark Energy Survey spanning $0.01\lt z \lt1.13$ anchored to the recent Baryon Acoustic Oscillation measurements from DESI spanning $0.30 \lt z_{\mathrm{eff}} \lt 2.33$. To trace cosmology to $z=0$, we use the third-, fourth- and fifth-order cosmographic models, which, by design, are agnostic about the energy content and expansion history of the universe. With the inclusion of the higher-redshift DESI-BAO data, the third-order model is a poor fit to both data sets, with the fourth-order model being preferred by the Akaike Information Criterion. Using the fourth-order cosmographic model, we find $H_0=67.19^{+0.66}_{-0.64}\mathrm{~km} \mathrm{~s}^{-1} \mathrm{~Mpc}^{-1}$, in agreement with the value found by Planck without the need to assume Flat-$\Lambda$CDM. However the best-fitting expansion history differs from that of Planck, providing continued motivation to investigate these tensions.

• The paper introduces the inverse distance ladder method by calibrating Type Ia supernovae with BAO data to bypass local Cepheid uncertainties.
• The study reports H0 = 67.19⁺⁰.⁶⁶₋₀.₆₄ km s⁻¹ Mpc⁻¹, consistent with Planck measurements and highlighting discrepancies with SH0ES results.
• The methodology refines cosmological measurements and paves the way for future research using model-independent techniques and next-generation BAO surveys.

An Updated Measurement of the Hubble Constant Using the Inverse Distance Ladder

This essay reviews the recent analysis presented in a paper by Camilleri et al., which focuses on measuring the Hubble constant ($H_0$) using a novel approach termed the inverse distance ladder. The paper utilizes data from the Dark Energy Survey Supernova Program and Baryon Acoustic Oscillations (BAO) measurements, aiming to provide an independent cross-examination of $H_0$ amidst existing discrepancies.

Methodology

The approach adopted by the authors revolves around calibrating the magnitudes of Type Ia supernovae (SNe Ia) using BAO data, rather than the more traditional method that relies on Cepheid variable stars for calibration. This technique bypasses potential systematic uncertainties associated with local calibrators by anchoring the supernovae to high-redshift data. The survey leverages a large dataset of 1829 supernovae spanning a redshift range of $0.01 < z < 1.13$ from the Dark Energy Survey and employs a cosmographic approach, which is model-independent with respect to the universe's energy content.

Results

One of the significant results from the paper is the determination of $H_0 = 67.19^{+0.66}_{-0.64}$ km s$^{-1}$ Mpc$^{-1}$ which is consistent with the Planck satellite's cosmic microwave background measurements. Interestingly, this value diverges from the SH0ES collaboration’s measurement of $H_0 = 73.04 \pm 1.04$ km s$^{-1}$ Mpc$^{-1}$, highlighting a prominent disparity in contemporary measurements of the Hubble constant. The analysis from Camilleri et al. showed the $4^{\text{th}}$ order cosmographic model to be the most favorable in fitting the data, markedly improving fit relative to lower-order models.

Implications

From a theoretical standpoint, this paper reinforces the alignment of high-redshift measurement techniques with early universe physics as interpreted by the Planck results. Practically, the use of BAO as a 'ruler' in the inverse distance ladder method presents a robust avenue for future investigations into cosmological expansion rates, allowing researchers to potentially narrow down on the causes behind $H_0$ tension.

Future Directions

Further exploration and refinement of the inverse distance ladder approach could augment our understanding of cosmic expansion. The paper's approach can be extended with more precise and extensive BAO data from next-generation surveys like DESI, which would enhance the accuracy of these cosmological measurements. Moreover, the continued development of model-independent methods and additional high-redshift anchors may provide crucial insights both for the Hubble constant and broader cosmological models, particularly those exploring deviations from the standard model that might address the noted inconsistencies.

In conclusion, Camilleri et al.'s work contributes a valuable perspective to the continuing discourse on the value of the Hubble constant, emphasizing the need for alternative methodologies in addressing the current cosmic conundrums. Their application of the inverse distance ladder through the cosmographic expansion reaffirms its potential utility in unraveling the universe's rate of expansion, while simultaneously inviting further scrutiny and validation from the cosmological community.