The 21-cm forest probe may unlock secrets of early universe, nature of dark matter

The thriller of the formation of the primary galaxies within the universe is a puzzle for researchers. The character of dark matter can be one of the vital essential mysteries confronted by elementary physicists. Nonetheless, understanding the character of dark matter—for instance, whether or not it’s chilly or heat—and its subsequent impact on the formation of the primary galaxies is a large problem.

Now, a joint analysis group from Northeastern College (China) and the Nationwide Astronomical Observatories of the Chinese language Academy of Sciences (NAOC) has proposed utilizing a brand new probe to attempt to make clear the character of dark matter and the early formation of galaxies concurrently. The group’s examine was printed in Nature Astronomy on July 6.

A method of understanding dark matter is to attempt to measure the mass of dark matter particles by means of cosmological observations of small-scale constructions. However detecting small-scale constructions wherein no star formation has ever occurred is troublesome, particularly in the course of the cosmic dawn. Luckily, atomic hydrogen gasoline in and round these darkish, small constructions from cosmic daybreak creates 21-cm absorption lines alongside the traces of sight between Earth and high-redshift radio level sources. These absorption traces are recognized collectively because the 21-cm forest.

The 21-cm forest probe is a theoretical idea that has been proposed for greater than 20 years, with the aim to seek for gasoline temperatures and doubtlessly for dark matter properties in the course of the cosmic daybreak. To date, scientists haven’t tried to truly use the probe attributable to quite a few challenges, together with extraordinarily weak indicators, the issue in figuring out high-redshift background sources, and the degeneracy between the mass of dark matter particles and the heating impact, which might forestall the probe from constraining both the particle mass or the heating impact from the primary galaxies.

Just lately, although, numerous high-redshift radio-loud quasars have been found. As well as, development on the Sq. Kilometer Array (SKA)—a global initiative to construct the world’s largest radio telescope—started final December. Each these developments recommend that utilizing the 21-cm forest probe will quickly be possible.

Impressed by energy spectrum analyses extensively utilized in cosmological probes, the NAOC researchers realized that the distinctive scale-dependences of the indicators brought on by the nice and cozy dark matter impact and the heating impact, respectively, could possibly be used to statistically extract key options to differentiate the 2 results.

On this examine, the researchers proposed a novel statistical answer to concurrently resolve the weak sign drawback and the degeneracy drawback, by measuring the one-dimensional (1-D) energy spectrum of the 21-cm forest. The sign scale-dependence revealed by the amplitude and form of the 1-D energy spectrum makes the 21-cm forest probe a viable and efficient technique of concurrently measuring dark matter properties and the thermal historical past of the universe.

“By measuring the one-dimensional energy spectrum of the 21-cm forest, we cannot solely make the probe really possible by growing the sensitivity, but in addition present a method to distinguish the consequences of heat dark matter fashions and early heating course of,” stated Xu Yidong, corresponding creator of the examine. “We will kill two birds with one stone.”

In eventualities the place cosmic heating is just not too extreme, SKA Section 1’s low-frequency array might be able to successfully constraining each dark matter particle mass and gasoline temperature. In instances the place cosmic heating is extra important, using a number of background radio sources throughout SKA Section 2 will allow strong detection capabilities.

The 21-cm forest presents a viable means for constraining dark matter at redshift ranges past the attain of different observations. By measuring the heating degree, the 21-cm forest gives a method to constrain the spectral properties of the primary galaxies and the primary black holes, in order to make clear the character of the primary vivid objects within the universe. Utilizing the 21-cm forest probe will function an indispensable avenue for advancing our understanding of the early universe and peering into the mysteries of each dark matter and the primary galaxies.

Since software of the 21-cm forest probe is intently tied to observations of high-redshift background radio sources, the subsequent step can even contain figuring out extra radio-bright sources on the cosmic daybreak (equivalent to radio-loud quasars and gamma-ray burst afterglows) that may be adopted up within the SKA period.