FAST discovers largest atomic gas structure around a galaxy group

Atomic fuel is the essential materials that every one galaxies are shaped from. The evolution of galaxies is usually a process of accreting atomic fuel from the intergalactic medium after which changing it into stars.

For that reason, commentary and exploration of atomic fuel in and round galaxies is essential to the examine of galaxy formation and evolution fashions. Essentially the most direct technique of exploring atomic fuel is thru commentary of the 21-cm superb construction line emission of atomic hydrogen within the radio waveband.

Just lately, utilizing the 5-hundred-meter Aperture Spherical Telescope (FAST) 19-beam receiver, a world workforce led by Xu Cong, a researcher from the Nationwide Astronomical Observatories of the Chinese language Academy of Sciences (NAOC), carried out deep mapping observations of 21-cm line emission in a area across the well-known compact group of galaxies “Stephan’s Quintet,” and found a really giant atomic fuel construction with a size of about 2 million light years (about 20 instances the scale of the Milky Way).

Their findings have been printed in Nature on Oct. 19.

FAST is at the moment the biggest and most delicate single-dish radio telescope on the earth, and its 19-beam receiver is the biggest L-band multibeam feed array for 21-cm line observations. The total commissioning of the FAST 19-beam receiver opened a brand new window on atomic fuel within the universe, notably for low density diffuse fuel far-off from galaxies.

“That is the biggest atomic fuel construction ever discovered round a galaxy group,” stated Xu. The observations reached a sensitivity of 1σ=4.2×10¹⁶ cm^-2 per channel (Δv=20 km s^-1; angular-resolution=4′), making them at the moment probably the most delicate observations of atomic hydrogen 21-cm line emission at this angular decision.

Ever since its discovery by the French astronomer Edouard Stephan in 1877, Stephan’s Quintet has continued revealing puzzles associated to the advanced internet of galaxy-galaxy and galaxy-intragroup medium interactions within the group.

The brand new observations present that large-scale, diffuse, low density fuel (with a column identification lower than 10¹⁸ cm^-2) exists far-off from the middle of the group, and it’s possible that the fuel has been there for ~1 giga years. The observations problem the present concept of galaxy-group formation/evolution as a result of it isn’t clear how the low-density atomic gas can survive ionization by the intergalactic UV background on such a very long time scale.