English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We analyze the possibilities of detecting a signal in the hydrogen 21 cmline, which was formed in the early universe during the Dark Ages, using theUkrainian radio telescopes UTR-2 and GURT of the National Academy of Sciencesof Ukraine. As a result of cosmological expansion, this line is shifted to thedecameter range of wavelengths ($\lambda_{obs}\approx18$ m,$\nu_{obs}\approx16$ MHz) and is in the band of operating frequencies of thesetelescopes. The brightness temperature of the predicted sky-averaged globalsignal ranges from $\sim-0.08$ to $\sim0.02$ K, depending on the cosmologicalmodel. Such a weak signal is a big challenge even for the world's largest radiotelescope in the decameter wavelength range UTR-2, since the signal level ofthe synchrotron radiation of the Galaxy at these frequencies is 20,000-40,000K. The paper highlights the peculiarities of spectroscopy at decameter waves,interfering factors of natural and instrumental origin and ways to eliminatethem in order to reliably detect the signal in the 21 cm line, which can becomean important source of information both about the environment in which thefirst stars and galaxies were born, and about the nature of dark matterparticles and the magnitude of primordial magnetic fields. It was concludedthat the detection of such a signal using the most sensitive radio telescopesof the decameter wavelength range is quite possible (with a frequencyaccumulation of 25 MHz, the detection time will be ~50 days) and can beimplemented in the coming years of peace in Ukraine.

On the Possibility of Detecting a Global Signal in the Line of the Hyperfine Structure of Hydrogen from the Dark Ages