Work

Unveiling the Dark Ages: A New Pathway Using Tomographical 21 cm Cosmic Microwave Background Cross-correlations

Year: 2026

Type: article

Abstract: The cosmic dark ages are comovingly adjacent to the last-scattering surface, and this proximity, in conjunction with the spectral redness of the primordial potential, makes the cosmic microwave background (CMB) and the dark ages measurably correlated on the largest scales. We present simulated all-sky 21 cm maps of the associated density fluctuations in the dark ages at z < 200 and provide tomographical deconstructions of (foreground-contaminated) 21 cm fluctuation maps that we correlate with mock CMB maps of primordial temperature fluctuations. We find that utilizing all tomographic information of a dark ages survey allows us to improve the variance of the 21 cm cross-correlation by several orders of magnitude over the case of 21 cm autocorrelations with foregrounds. Inclusion of cross-correlations suppresses the foreground mean and transforms the contaminating foreground into a variance term that averages down with mode count. Our results pioneer a pathway toward ultrahigh-precision cosmology of the dark ages via low-frequency lunar farside radio arrays.

Source: The Astrophysical Journal Letters

DOI: 10.3847/2041-8213/aea411

Authors: Joshua J. Hibbard, Joseph Silk

Institutions: University of Colorado Boulder, University of California System, Johns Hopkins University, Sorbonne Université, University of Oxford

Language: English

Topic: Radio Astronomy Observations and Technology

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,400

Funder: University of Colorado Boulder