Astronomers combine the power of 64 telescopes to observe the structure of the universe

South Africa’s MeerKAT telescope. Credit: South African Radio Astronomy Observatory (SARAO)

An international team of astronomers has combined the power of 64 radio telescope dishes for the first time to detect the faint signatures of neutral hydrogen gas across cosmological scales.

The feat was accomplished using the South Africa-based MeerKAT telescope, a precursor to the world’s largest radio observatory, the SKA Observatory (SKAO), which will examine the universe in unprecedented detail.

A primary goal of the SKAO is to understand the evolution and contents of the universe, along with the mechanisms driving its accelerated expansion. One way to achieve this is to observe the structure of the Universe at the largest scales. On these scales, entire galaxies can be viewed as discrete points, and analysis of their distribution reveals clues about the nature of gravity and mysterious phenomena such as dark matter and dark energy

Radio telescopes are a fantastic tool for this because they can detect radiation with a wavelength 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 investigate the total distribution of matter in the universe.

The SKAO, whose headquarters are in Jodrell Bank, Cheshire, is currently under construction. However, pathfinder telescopes, such as the 64-dish array MeerKAT, are already out there to guide the design. Based in the Karoo Desert and operated by the South African Radio Astronomy Observatory (SARAO), MeerKAT will eventually become part of the entire SKAO.

MeerKAT and the SKAO will act primarily as interferometers, combining the array of dishes into one giant telescope capable of imaging distant objects at high resolution. “However, the interferometer will not be sensitive enough for the largest scales of most interest to cosmologists studying the Universe.” explained the co-lead author of the new research paper, Steven Cunnington. “So we’re instead using the array as a collection of 64 individual telescopes, allowing them to map the massive amounts of air needed for cosmology.”

“For many years I have worked to predict the future capacity of the SKAO. Now to get to a stage where we develop the tools we need and demonstrate their success with real data is incredibly exciting. This marks just the beginning of what we hope will be a continuous showcase of results that advance our understanding of the Universe.”

Steven Cunnington

The single-dish mode was driven by a team from the University of the Western Cape, with several observations already conducted with MeerKAT. This ambitious project involves many other institutions across four continents. In the new study submitted for publication, a team consisting of Manchester-based astronomers Steven Cunnington, Laura Wolz and Keith Grainge presents the first-ever cosmological detection using this single-dish technique.

The new detection is of a shared cluster pattern between MeerKAT’s maps and galaxy positions determined by the Anglo-Australian Optical Telescope. Because these galaxies are known to track the total matter of the Universe, the strong statistical correlation between the radio maps and the galaxies shows that the MeerKAT telescope detects large-scale cosmic structure. This is the first time such a detection has been made using a multi-dish array acting as individual telescopes. The entire SKAO will rely on this technique and this therefore marks an important milestone in the cosmology science case roadmap with the SKAO.

“This detection has been done with only a small amount of pilot research data,” Steven Cunnington revealed. “It’s encouraging to imagine what will be achieved as MeerKAT continues to make larger and larger observations.

“For many years I have worked to predict the future capacity of the SKAO. Now to get to a stage where we develop the tools we need and demonstrate their success with real data is incredibly exciting. This marks just the beginning of what we hope will be a continuous showcase of results that advance our understanding of the Universe.”

Reference: “HI-intensity mapping with MeerKAT: power spectrum detection in cross-correlation with WiggleZ galaxies” by Steven Cunnington, Yichao Li, Mario G. Santos, Jingying Wang, Isabella P. Carucci, Melis O. Irfan, Alkistis Pourtsidou, Marta Spinelli, Laura Wolz , Paula S. Soares, Chris Blake, Philip Bull, Brandon Engelbrecht, José Fonseca, Keith Grainge and Yin-Zhe Ma, June 3, 2022, Astrophysics > Cosmology and non-galactic astrophysics
arXiv:2206.01579


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