“21 cm line” observed from a galaxy 13.3 billion light years away Significantly updated the farthest record | sorae Portal site to the universe

One of the wavelengths observed in radio astronomy“21 cm line”there is. This is the spectral line emitted by a neutral hydrogen atom and is so called because its wavelength is approximately 21 cm.

Hydrogen is the most abundant substance in the universe, and the 21 cm line can be observed even with radio telescopes on the ground. Since the value of the spectral line emitted from hydrogen itself is invariant, the observed wavelength shift can be regarded as the result of the Doppler effect due to the movement of the celestial body itself and the expansion of the universe. The 21 cm line is an excellent and important observational target for studying the distribution and motion of matter in the universe. to the extent that it is strictly prohibited.

The reason why the 21cm line is weak is that individual hydrogen atoms rarely satisfy the conditions for emitting the 21cm line. Therefore, it is extremely difficult to detect individual 21 cm rays from galaxies farther than about 5 billion light-years (comoving distance, same below). It was a galaxy called J100054.83+023126.2.

[▲ Figure 1: The giant meter-wave radio telescope in Pune, India, observes radio waves in the 21 cm line and longer wavelengths. Due to the nature of the radio waves to be observed, it has a unique appearance because it can receive radio waves with wires stretched between the frameworks without having a smooth reflective surface. (Image Credit: Giant Meterwave Radio Telescope / Tata Institute of Fundamental Research / National Center for Radio Astrophysics)]

A research team led by Arnab Chakraborty of McGill University and Nirupam Roy of the Indian Institute of Science is a radio telescope in Pune, India.“Giant Metric Radio Telescope (GMRT)”In the data archive of , we observed 21cm rays from a distant galaxy that far exceeded any previous records.this galaxy「SDSS J0826+5630」teeth,A galaxy that existed 8.9 billion years ago and is 13.3 billion light years away from Eartham. This means that the galaxy existed 4.9 billion years after the birth of the universe. SDSS J0826+5630 is presumed to be an active star-forming galaxy typical of the young universe.

The key to the detection of the 21 cm line this time was“Gravitational lens effect”am. According to general relativity, gravity is described as a distortion of space-time. Light has the property of traveling straight through space, but if space-time is distorted, it will follow that distortion. If there is another galaxy that is the source of space-time distortion between us and the target galaxy, the light that is deflected may gather at the observer. This phenomenon is called the gravitational lensing effect because it looks as if a convex lens is used to focus the light.

[▲ Figure 2: The red dot in the center of the image is SDSS J0826+5630, which was observed this time. (Image credit: Chakraborty & Roy)]

In the case of SDSS J0826+5630, another galaxy between us and SDSS J0826+5630 causes gravitational lensing,Increases signal strength by approximately 30 timesIt was done. Without the gravitational lensing effect, we would not have been able to observe the 21 cm line from such a distant galaxy.

In addition, SDSS J0826+5630 met the conditions for accurately estimating the total mass of the star. Luckily given the general difficulty in accurately estimating the total mass of stars in distant galaxies, it is estimated to be about 3.8 billion times that of the Sun. In addition, by measuring the 21 cm line, we were able to estimate the mass of the hydrogen gas covering the galaxy to be about 9 billion times that of the Sun. This value corresponds to almost twice the total mass of the star. By estimating the mass of hydrogen gas, which does not shine like stars, we obtained information useful for estimating the structure of galaxies where star formation is active.

In addition, from the analysis results of SDSS J0826+5630, it is estimated that the intensity of the 21 cm line of a distant galaxy strongly depends on the amount of neutral hydrogen atoms contained in the galaxy. The farther the galaxy is from the earth, the weaker the signal strength of the signal that reaches the earth. It is estimated that there is a tendency to include it, so it may compensate for the decrease in signal strength. The results of this study arePossibility of finding 21cm lines in other galaxies with gravitational lensingdoing.

Source

• Arnab Chakraborty & Nirupam Roy. – “Detection of H I 21 cm emission from a strongly lensed galaxy at z ∼ 1.3”. (Monthly Notices of the Royal Astronomical Society)
• News Staff. – “Astronomers Detect Radio Signal from Strongly Gravitationally Lensed Galaxy”. (SciNews)
• Ximena Fernandez, et.al. – “Highest Redshift Image of Neutral Hydrogen in Emission: A CHILES Detection of a Starbursting Galaxy at z = 0.376”. (The Astrophysical Journal Letters)

Text: Riri Ayae