The Five Hundred Meter Aperture Spherical Radio Telescope (FAST) is a radio telescope located in southwest China. It consists of a fixed plate 500 m in diameter built in a natural depression in the landscape. It is the world’s largest full-aperture radio telescope.
The five hundred meter aperture spherical radio telescope (FAST) is the largest telescope with the highest sensitivity in the world. Detection of extragalactic neutral hydrogen is one of FAST’s important scientific objectives.
Recently, an international research team led by Dr. CHENG Cheng of the South American Astronomical Center of the Chinese Academy of Sciences (CASSACA) observed four extragalactic galaxies using the 19-beam FAST receptor and detected the emission of the line neutral hydrogen from three targets with only five minutes of exposure each. This is the first FAST publication to detect extragalactic neutral hydrogen.
The research work was published in Astronomy and astrophysics letters.
Color optical images of the four galaxies for FAST observation. The red outlines are the previous CO observation of ALMA. The white spectra in each panel are the FAST results. Credit: CASSACA
Neutral hydrogen gas is the most widespread baryon in galaxies, while CO-traced cold gas is most concentrated in a galaxy center (red outline in Figure 1). “With dynamic measurements of neutral hydrogen and CO, we can estimate the mass distribution of galaxies at different radii,” said Dr. CHENG, first author of the study.
The dynamic masses of these four galaxies estimated from the newly observed neutral hydrogen line were 10 times higher than the observed baryonic masses, indicating the contribution of dark matter.
On the other hand, the dynamic masses estimated using previous CO observations were equivalent to their observed baryonic masses. Therefore, the new FAST observation illustrated its ability to study dark matter in galaxies using the 21 cm neutral hydrogen emission line.
QUICK observation of these galaxies was an important part of an international research project, Valparaíso SOUL Line Emission Survey (VALS), led by Prof. Edo Ibar of the University of Valparaíso in Chile.
The VALES is a project of observing star-forming galaxies using first-class international facilities such as Sloan Digital Sky Survey (SDSS), Herschel Space Observatory, Atacama Large Millimeter Array (ALMA), Atacama Pathfinder Experiment telescope (APEX) and Very large telescope (VLT)
FAST, with unprecedented sensitivity, offers a unique opportunity to observe extragalactic neutral hydrogen and has therefore been added to the list of modern astronomical facilities used by this international collaboration.
Reference: “The atomic gas of star-forming galaxies at z ∼ 0.05 as revealed by the five hundred meter aperture spherical radio telescope” by Cheng Cheng, Edo Ibar, Wei Du, Juan Molina, Gustavo Orellana-Gonzáles, Bo Zhang, Ming Zhu, Cong Kevin Xu, Shumei Wu, Tianwen Cao, Jia-Sheng Huang, Roger Leiton, Thomas M. Hughes, Chuan He, Zijian Li, Hai Xu, Y. Sophia Dai, Xu Shao, and Marat Musin, June 29, 2020 , Astronomy and astrophysics letters.
DOI: 10.1051 / 0004-6361 / 202038483
