An international team of astronomers has for the first time combined the power of 64 radio telescope dishes to detect faint signatures of neutral hydrogen gas across cosmological timescales.
The feat was achieved using the South Africa-based MeerKAT Telescope, a precursor to the world’s largest radio observatory, the SKA Observatory (SKAO), which will probe the universe in unprecedented detail.
One of the main objectives of SKAO is to understand the evolution and content of the universe as well as the mechanisms that lead to its accelerated expansion. One way to do this is to observe the structure of the universe at the largest scales. At these scales, entire galaxies can be viewed as single points, and analysis of their distribution reveals clues to the nature of gravity and mysterious phenomena such as dark matter and dark energy.
Radio telescopes are a fantastic instrument for this since they can detect radiation at wavelengths of 21 cm generated by neutral hydrogen, the most abundant element in the universe. By analyzing 3D maps of hydrogen spanning millions of light-years, we probe the total distribution of matter in the universe.
The SKAO, headquartered in Jodrell Bank, Cheshire, is currently under construction. However, there are already pathfinder telescopes, such as the MeerKAT 64-antenna array, in place to guide its design. Based in the Karoo Desert and operated by the South African Radio Astronomy Observatory (SARAO), MeerKAT will eventually become part of the full SKAO.
MeerKAT and SKAO will primarily function as interferometers, where the array of dishes is combined into a giant telescope capable of imaging distant objects with high resolution. “However, the interferometer will not be sensitive enough at the largest scales of most interest to cosmologists studying the universe,” explained co-lead author of the new research paper, Steven Cunnington. “Therefore, we’re using the array instead as a collection of 64 individual telescopes that allows them to map the giant volumes of sky needed for cosmology.”
The single antenna mode of operation has been piloted by a team from the University of the Western Cape, with several observations already conducted with MeerKAT. This ambitious project involves many other institutions spread over four continents. In new research posted to arXiv and submitted for publication, a team that includes Manchester-based astronomers Cunnington, Laura Wolz and Keith Grainge, present the first-ever cosmological detection using this single-dish technique.
The new detection is that of a shared clustering pattern between MeerKAT maps and galaxy positions determined by the British-Australian Optical Telescope. As these galaxies are known to trace the overall matter of the universe, the strong statistical correlation between the radio maps and the galaxies shows that the MeerKAT telescope detects a large-scale cosmic structure. This is the first time such detection has been performed using an array of multiple dishes operating as individual telescopes. Full SKAO will build on this technique and therefore marks an important step in the roadmap for the science case of cosmology with SKAO.
“This detection was made with only a small amount of pilot survey data,” Cunnington revealed. “It’s encouraging to imagine what will be achieved as MeerKAT continues to make bigger and bigger observations.”
“For many years I have worked to predict the future capabilities of SKAO. Reaching a stage now where we are developing the tools we will need and demonstrating their success with real data is incredibly exciting. what we hope will be an ongoing showcase of results that will advance our understanding of the universe.”
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Steven Cunnington et al, HI intensity mapping with MeerKAT: cross-correlated power spectrum detection with WiggleZ galaxies, arXiv:2206.01579 [astro-ph.CO]arxiv.org/abs/2206.01579
Provided by the University of Manchester
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