Astronomers using the Nobeyama Radio Obeservatory (NRO) 45-m telescope found that high-density gas, the material for stars, accounts for only 3% of the total mass of gas distributed in the Milky Way. This result provides key information for understanding the unexpectedly low production rate of stars.
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| The high-density gas (right) is detected only in small parts of the low-density gas (left) [Credit: NAOJ] |
To interpret the discrepancy, observations which detect both of the high-density and low-density gas with high-spatial resolution and wide area coverage were needed. However, such observations are difficult, because the high-density gas structures are dozens of times smaller than the low-density gas structures.
The Milky Way survey project "FUGIN" conducted using the NRO 45-m telescope and the multi-beam receiver FOREST overcame these difficulties. Kazufumi Torii, a project assistant professor at NAOJ, and his team analyzed the big data obtained in the FUGIN project, and measured the accurate masses of the low-density and high-density gas for a large span of 20,000 light-years along the Milky Way. They revealed for the first time that the high-density gas accounts for only 3% of the total gas.
These results imply the production rate of high-density gas in the low-density gas clouds is small, creating only a small number of opportunities to form stars. The researcher team will continue working on the FUGIN data to investigate the cause of inefficient formation of the high-density gas.
These observation results were published as an on-line paper of the Publications of the Astronomical Society of Japan, and will be published as a special issue.
Source: National Institutes of Natural Sciences [July 25, 2019]
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