It is thought that the Universe went through an early period known as
the Dark Ages, during which gravity acted on the cosmic gas and
gradually drove the formation of the first stars, marking the
beginning of Cosmic Dawn around 100 million years after the Big
Bang. The most promising probes of these unexplored epochs are the
radio waves emitted by hydrogen atoms that filled the early Universe,
with extensive observational efforts underway to detect them. The new
study combines numerical simulations of complex gas physics with
large-scale cosmic maps in order to calculate the effect of the
development of dense gas clumps on the overall global (sky-averaged)
radio intensity. This effect presents a potential opportunity, since
the clumps are too small to be directly observed, while global
intensity observations are being actively pursued. The formation of
the gas clumps is driven by the gravitational pull of dark matter
nuggets, whose existence is predicted by standard theory but has not
been observationally confirmed. Thus, these findings open new avenues
for testing the nature of dark matter as well as processes that
occurred in the early Universe.
These two images show illustrative outputs from a numerical
simulation. The black and white image shows the distribution of dark
matter, which forms dense clumps shown in darker black. The color
image shows the corresponding distribution of gas temperature. Dense
dark matter nuggets pull in the ordinary (mostly hydrogen) gas due to
gravity, and the gas reaches high density and temperature (red areas,
and even higher temperatures shown as yellow). We predict that the
emission of radio waves from this hot gas changes the overall
intensity and pattern of radio waves on the sky, and this can be
observed with radio telescopes and used to study the nature of dark
matter.
