Prospects for cosmological research using hundred-meter-class radio telescopes: 21-cm intensity mapping survey strategies with QTT, JRT, and HRT

TL;DR

The paper evaluates the cosmological promise of 21 cm intensity mapping with three hundred-meter-class Chinese single-dish telescopes (QTT, JRT, HRT) using a Fisher-to-MCMC forecasting framework. By modeling the signal, noise, foregrounds, and instrument parameters, and computing BAO/RSD constraints on $D_A(z)$, $H(z)$, and $f\sigma_8(z)$, the study propagates these to ΛCDM and $w_0w_a$CDM parameters. The key result is that extending redshift coverage to $z_{\mathrm{max}}=1$ dramatically improves constraints, with the combined QTT+JRT+HRT achieving $\sigma(w_0)\approx0.094$ and $\sigma(w_a)\approx0.487$, outperforming DESI DR2. The work demonstrates the strong potential of coordinated hundred-meter-class IM surveys, especially when leveraging multi-beam/PAF capabilities to balance angular resolution and survey speed, and it provides actionable guidance for future survey design.

Abstract

Understanding dark energy requires precision measurements of the expansion history of the universe and the growth of large-scale structure. The 21 cm intensity mapping (21 cm IM) technique enables rapid large-area surveys that can deliver these measurements. China is constructing three hundred-meter-class single-dish radio telescopes, including the QiTai 110 m Radio Telescope (QTT), the 120 m Jingdong Radio Telescope (JRT), and the 120 m Huadian Radio Telescope (HRT), whose designs are well suited for 21 cm IM cosmology. We use a Fisher-to-MCMC forecasting framework to evaluate the baryon acoustic oscillations / redshift space distortions (BAO/RSD) measurement capabilities of QTT, JRT, and HRT and propagate them to dark-energy constraints in the $w_0w_a$CDM model. Our results show that achieving a redshift coverage up to $z_{\mathrm{max}} = 1$ is crucial for fully realising the potential of hundred-meter-class single-dish telescopes for 21 cm cosmology. If all three telescopes carry out 21 cm IM surveys over the same redshift range up to $z_{\mathrm{max}}=1$ and combine their BAO/RSD measurements, QTT+JRT+HRT yield $σ(w_0)=0.094$ and $σ(w_a)=0.487$, providing tighter constraints than DESI DR2 results.

Figures (5)

• Figure 1: Redshift evolution of the transverse wavenumber $k_\perp$ coverage for different instruments, with colored shaded regions showing the minimum and maximum $k_\perp$ accessible at each redshift, dark gray dashed lines marking the BAO $k_\perp$ range and the shaded gray region denoting superhorizon scales with $k_H = 2\pi / r_H$.
• Figure 2: Relative errors on $D_\mathrm{A}(z)$, $H(z)$, and $f\sigma_8(z)$ for 21-cm IM with QTT, JRT, and QTT+JRT+HRT for $z\in[0,0.4]$ using the current designs.
• Figure 3: $1\sigma$ and $2\sigma$ constraints on $\Lambda$CDM (left) and $w_0w_a$CDM (right) from simulated 21-cm IM with QTT, JRT, and QTT+JRT+HRT (restricted to $z\le0.4$), compared with DESI DR2.
• Figure 4: Relative errors on $D_\mathrm{A}(z)$, $H(z)$, and $f\sigma_8(z)$ for 21-cm IM with QTT, JRT, and QTT+JRT+HRT for $z\in[0,1]$, assuming JRT and HRT are extended to $z_{\max}=1$.
• Figure 5: $1\sigma$ and $2\sigma$ constraints on $\Lambda$CDM (left) and $w_0w_a$CDM (right) from simulated 21-cm IM with QTT, JRT, and QTT+JRT+HRT for the extended configuration with $z_{\max}=1$, compared with DESI DR2.