FAST Sheds Light On Extragalatic Dark Matter

FAST, the world’s largest telescope, has detected neutral hydrogen emission from extragalactic galaxies for the first time.

AsianScientist (Aug. 25, 2020) – Using the largest telescope in the world—the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in China—researchers have detected neutral hydrogen line emissions from galaxies beyond our own, shedding light on the nature of dark matter. These findings have been published in Astronomy & Astrophysics Letter.

While there are over 200 billion stars in our own galaxy, the Milky Way is just one of billions of galaxies in the observable universe. Despite their great distance from Earth, we can find out more about these extragalatic galaxies with highly sensitive telescopes that can measure a spectrum of electromagnetic radiation known as the hydrogen line.

“With dynamical measurements of neutral hydrogen and (CO) carbon monoxide, we can estimate the mass distribution of galaxies at different radii,” said study first author Dr. Cheng Cheng of the Chinese Academy of Sciences South America Center for Astronomy

Using the FAST telescope, Cheng and his team were able to observe four extragalactic galaxies and estimate their dynamical masses, which were found to be ten times higher than the observed baryon masses—an indication of the contribution of dark matter.

On the other hand, dynamical masses estimated using previous CO observations were equivalent to their observed baryon masses, illustrating how FAST’s ability to detect the neutral hydrogen 21cm emission line could be used to study dark matter in galaxies.

The FAST observation of these galaxies was an important part of an international research project called the Valparaíso ALMA Line Emission Survey (VALES), which is led by Professor Edo Ibar from Valparaíso University, Chile. VALES is involved in observing star-forming galaxies using international facilities such as the Sloan Digital Sky Survey, Herschel Space Observatory, Atacama Large Millimeter Array, Atacama Pathfinder Experiment Telescope and Very Large Telescope.

The article can be found at: Cheng et al. (2020) The Atomic Gas of Star-forming Galaxies at z ∼ 0.05 as Revealed by the Five-hundred-meter Aperture Spherical Radio Telescope.


Source: Chinese Academy of Sciences; Photo: NASA/Unsplash.
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