Forecasts on Interacting Dark Energy from 21-cm Angular Power Spectrum with BINGO and SKA observations

Abstract

Neutral hydrogen (HI) intensity mapping is a promising technique to probe the large-scale structure of the Universe, improving our understanding on the late-time accelerated expansion. In this work, we first scrutinize how an alternative cosmology, interacting dark energy (IDE), can affect the 21-cm angular power spectrum relative to the concordance $\Lambda$CDM model. We re-derive the 21-cm brightness temperature fluctuation in the context of such interaction and uncover an extra new contribution. Then we estimate the noise level of three upcoming HI intensity mapping surveys, BINGO, SKA1-MID Band1 and Band2, respectively, and employ a Fisher matrix approach to forecast their constraints on the IDE model. We find that while $\text{Planck}$ 2018 maintains its dominion over early-Universe parameter constraints, BINGO and SKA1-MID Band2 put complementary bounding to the latest CMB measurements on dark energy equation of state $w$, the interacting strength ${\lambda }_i$ and the reduced Hubble constant $h$, and SKA1-MID Band1 even outperforms $\text{Planck}$ 2018 in these late-Universe parameter constraints. The expected minimum uncertainties are given by SKA1-MID Band1+$\text{Planck}$: $\sim 0.34\%$ on $w$, $\sim 0.22\%$ on $h$, $\sim 0.64\%$ on HI bias $b_{\mathrm{HI}}$, and an absolute uncertainty of about $3\times 10^{-4}$ ($7\times 10^{-4}$) on ${\lambda }_1$ (${\lambda }_2$). Moreover, we quantify the effects from systematics of the redshift bin number, redshift-space distortions, foreground residuals and uncertainties on the measured HI fraction, ${\Omega }_{\mathrm{HI}}(z)$. Our results indicate a bright prospect for HI intensity mapping surveys in constraining IDE, whether on their own or further by synergies with other measurements.

Comments: 20 pages, 13 figures, 9 tables, accepted for publication in MNRAS