Radio Sky Will Tell Us About Dark Energy express
The Universe is expanding, and galaxies are flying apart like raisins in rising dough. But since the late 1990s, we've known that this expansion is accelerating. What force is pushing galaxies apart faster and faster is one of physics' greatest mysteries. It's called dark energy, and it makes up about 70% of everything in the cosmos.
The BINGO radio telescope in Brazil will hunt for clues in the distribution of hydrogen — the most abundant element in the Universe. Hydrogen emits radio waves at a wavelength of 21 centimeters, and by measuring their shift, scientists can infer the distance to gas clouds. This way, they'll build a three-dimensional map of the Universe's large-scale structure — a giant web of galaxies and voids.
The authors of the new study simulated how BINGO would see these oscillations, accounting for interference from our Galaxy and receiver noise. They found that adding the telescope's data to Planck satellite measurements narrows the allowed range of cosmological parameters by about 60% compared to Planck alone. It's like swapping a tailor's tape for a laser rangefinder: same measurements, but far greater precision.
This approach will not only refine the parameters of the Universe but also track how the amount of hydrogen has changed over the past billions of years. And crucially, it will help us better understand how dark energy behaves: whether it's constant, like Einstein's cosmological constant, or whether its properties have changed over time.
Original abstract
as written by the authors arXiv:2601.10152
Context. Building on the transformative success of optical redshift surveys, the emerging technique of neutral hydrogen (HI) intensity mapping (IM) offers a novel probe of large-scale structure (LSS) growth and the late-time accelerated expansion of the universe. Aims. We present cosmological forecasts for the Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO), a pioneering HI IM experiment, quantifying its potential to constrain the Planck-calibrated $$\Lambda$$CDM cosmology and extensions to the $$w_0w_a$$CDM dark energy model. Methods. For BINGO's Phase~1 configuration, we simulate the HI IM signal using a lognormal model and incorporate three dominant systematics: foreground residuals, thermal noise, and beam resolution effects. Using Bayesian inference, we derive joint constraints on six cosmological parameters ($$\Omega_b h^2$$, $$\Omega_c h^2$$, $$100\theta_s$$, $$n_s$$, $$\ln 10^{10} A_s$$, and $$\tau_r$$) alongside 60 HI parameters ($$b_{\rm HI}^i$$, $$\Omega_{\rm HI}^i b_{\rm HI}^i$$) across 30 frequency channels. Results. Our results demonstrate that combining BINGO with the Planck 2018 CMB dataset tightens the confidence regions of cosmological parameters to $$\sim$$40\% the size of those from Planck alone, significantly improving the precision of parameter estimation. Furthermore, BINGO constrains the redshift evolution of HI density and delivers competitive measurements of the dark energy equation of state parameters ($$w_0$$, $$w_a$$). Conclusions. These results demonstrate BINGO's potential to extract significant cosmological information from the HI distribution and provide constraints competitive with current and future cosmological surveys.
The 21-centimeter wavelength is hydrogen's natural "radio beacon." Even if a gas cloud is billions of light-years away, its signal can be picked up by an ordinary radio antenna — if it's sensitive enough.