New $H(z)$ measurement at Redshift = 0.12 with DESI Data Release 1

TL;DR

The paper addresses a cosmology-independent measurement of the Hubble parameter by applying the cosmic chronometer method to DESI DR1 galaxies. It leverages full-spectrum fitting with a modified BAGPIPES framework to jointly fit spectra and photometry for >$3{,}000$ massive, passively evolving galaxies, deriving accurate stellar ages and SFHs without cosmological priors. By constructing median age–redshift relations in mass bins and using differential age methods, the study computes $H(z)$ at $z=0.12$ as $71.33$ km s$^{-1}$ Mpc$^{-1}$ with a total uncertainty of $4.20$ km s$^{-1}$ Mpc$^{-1}$, and demonstrates robustness against binning and SFH choices. The results are consistent with ΛCDM and prior CC measurements, underscoring the effectiveness of the cosmic chronometer approach with DESI DR1 data and guiding future work with advanced SPS models and next-generation surveys.

Abstract

The Hubble parameter ($H(z)$) is a function of the redshift and a reliable measurement is very important to understand the expansion history of the Universe. In this work, we perform full-spectrum fitting using BAGPIPES on more than four thousand massive, passively evolving galaxies released by the DESI collaboration to estimate their cosmological-independent stellar ages and star-formation histories, and derive a new measurement of $H(z=0.12)=71.33 \pm 4.20~{\rm km~s^{-1}~Mpc^{-1}}$, which is well consistent with those derived in other ways.

Figures (7)

• Figure 1: An typical CC (TARGETID = 2851244993413120) fitting result. Spectrum and photometry observation data are shown in blue, best-fit results are shown in orange. Gray area are masked when fitting.
• Figure 2: Comparison of the TARGETID = 2851244993413120's reconstructed star formation history profiles between the DED (dark blue) and DPL (light blue) models. The horizontal axis represents the lookback time in Gyr, and the vertical axis shows the star formation rate (SFR) in $M_{\odot} \text{ yr}^{-1}$. In both cases, the solid lines indicate the median of the posterior distribution, while the shaded regions represent the $1\sigma$ uncertainties.
• Figure 3: Distributions of the inferred physical properties for our CC sample, derived from BAGPIPES. The panels show the distribution of posterior median values for the spectroscopic redshift, stellar velocity dispersion ($\sigma_{\rm vel}$), stellar age, sSFR ($\log_{10}(\rm sSFR/yr^{-1})$), stellar mass ($\log_{10}(M_{\star}/M_{\odot})$) and metallicity relative to solar ($Z/Z_{\odot}$), respectively.
• Figure 4: Redshift distribution of stellar age, star formation timescale ($\tau$), metallicity, and logarithmic stellar mass ($\log_{10}(M_{\star}/M_{\odot})$) obtained from the full-spectrum fitting of our CC sample. Each galaxy is color-coded by its velocity dispersion ($\sigma_{\rm vel}$). The black dashed line in the first panel is the age--redshift relation predicted by the 2020AA...641A...6P$\Lambda$CDM model.
• Figure 5: Median-binned age--redshift relations for our baseline results. The blue and orange points represent the lower and higher mass bins divided by the median value. For illustration, we also present the redshift $z_f$ of galaxy formation (gray dashed lines) within the $\Lambda$CDM model by 2020AA...641A...6P.