The world’s first discovery of a new appearance of a galaxy drawn by ultra-contrast observations using the ALMA telescope | Press release from the Department of Public Relations of Kogakuin University

A research team led by Associate Professor Shinya Waite (Education Promotion Organization) of Kogakuen University (President: Shinichiro Ito, Location: Shinichiro Ito, Hachioji City, Tokyo) has observed a galaxy called 3C273 with the ALMA telescope which is special. As a result of data analysis, we have discovered for the first time in the world that there is a faint radio emission in the galaxy for tens of thousands of light years.

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Fantasy view of a giant galaxy with a high-energy jet. Credit: ALMA (ESO/NAOJ/NRAO)

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3C 273 observed in this study is the central core of the galaxy at a distance of 2.4 billion light-years from Earth, a celestial body of a genus called quasars. Its identity is a massive black hole that produces intense light energy by swallowing surrounding material. 3C 273, also the first quasar discovered in the world, emits the strongest radio waves of quasars. For this reason, it is a “well known” object that has been studied for decades and is often observed by the ALMA telescope as a reference for the location of the sky. For radio observation, 3C 273 is a lighthouse-like orb.

If you look directly into the headlights of a car, your eyes will be dazzled and it will be difficult to see what is going on around you, but the same thing happens with a telescope. The ability to detect both bright and dark objects at the same time is called the dynamic range, and the ALMA telescope can accurately measure radio waves if the difference in brightness is several hundred times the dynamic range. Since the dynamic range of a general digital camera is several thousand times, it can be said that a radio telescope is not very good at observing celestial bodies with a large difference in brightness.

3C273 is an orb so bright that the eyes of a telescope sparkle. Despite being known as the best quasar in the sky for a long time, little was known about the appearance of a darker galaxy (the parent galaxy) because the center 3C273 itself was so bright. In analyzing the monitoring data, the research team applied a method called self-calibration, which uses the brightness of the 3C 273 itself as a standard for radio wave strength, correcting for radio wave fluctuations with frequency and time. To make the orb’s radio waves, we suppressed the leakage to the surroundings and noise as much as possible. As a result, we achieved a dynamic range of up to 85,000 times and succeeded in photographing even dark areas. This is the highest dynamic range ever obtained from extragalactic observations with the ALMA telescope.

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Quasar 3C273 observed by the Hubble Space Telescope (left figure)[1][2]…because it is so bright, the light scattered in the telescope leaks radially. In the lower right, you can see the high-energy jet emanating from the core.

Radio image from 3C273 observed by ALMA (right figure). However, the bright part is thrown in the center. The lightly scattered radio wave radiation around 3C273 was detected this time much weaker than the jet extending to the lower right.

Credit： Komugi et al. NASA/ESA Hubble Space Telescope

As a result of achieving a high dynamic range, we discovered that there is a previously unknown radio frequency radiation around 3C 273 that is faintly spread over tens of thousands of light years throughout the parent galaxy (Fig. If radio radiation is usually present around quasars, it is due to the ultra-fast jets emitted by the quasars or “synchrotron radiation” due to large-scale star-forming activity in the parent galaxy. 3C273 also emits a powerful jet in a certain direction from the center. Synchrotron radiation is characterized by a change in its intensity depending on the observed frequency, but the faint radioactive radiation detected in this study does not change depending on the frequency. As a result of examining various possibilities, it was found that this radio wave radiation is called “heat radiation” generated by the intense light from 3C 273 that illuminates the interstellar medium of the parent galaxy. It is the first time in the world that thermal radiation from gas illuminated by the galactic center has been found over a wide range of tens of thousands of light years. It has been overlooked for decades because it is not “dark by the lighthouse” but “beacon by the light”.

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Why is this discovery important? Until now, whether star formation in the parent galaxy is hindered by the effects of active galactic centers such as quasars has been a major problem in galactic astronomy. Hydrogen gas is required for star formation. If the quasar’s powerful light destroys (ionizes) the gas, it will prevent star formation. In order to check whether such a thing really occurs in quasars, it has been common practice to observe visible light and directly observe ionized gas. However, the mechanism by which ionized gas emits visible light is complex, and it is difficult to estimate the amount of ionized gas because the light is absorbed by dust in interstellar space. The thermal radiation observed in this study is characterized by a simple radio wave emission mechanism and is not dampened by dust. This makes it easy to estimate how much ionized gas is in the parent galaxy. In this study, 7% or more of the light from 3C 273 was found to be absorbed by hydrogen gas in the parent galaxy. It was found that the ionized gas produced by this is from 10 to 100 billion times the mass of the Sun, but on the other hand, there is also a large amount of molecular hydrogen gas in the state just before star formation, star formation like a whole galaxy. I also found that it did not appear to be clogged.

“This research provides a new method by observing radio waves to the subject of the research conducted by observing visible light. By applying the same method to other quasars in the future, the galaxy and its nucleus, it is hoped that we will gain a better understanding of how these factors affect each other and its development,” says Shinya Witt, Associate Professor (Education Promotion Organization, College of Engineering).

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paper title

Detection of millimeter-spanning emission in the 3C273 host galaxy and its effects on QSO feedback via ALMA high dynamic range imaging.

Publishing magazine

Astrophysical Journal, Vol. 930, Issue 3 (May 2022)

https://doi.org/10.3847/1538-4357/ac616e

researcher

Wheat Shinya (Kogakuen University), Yoshiki Toba (National Astronomical Observatory of Japan, Kyoto University), Yoshiki Matsuoka (Ehime University), Toshiki Saito (National Astronomical Observatory of Japan, Nihon University), Takutoki Yamashita (National Astronomical Observatory of Japan)

This research was supported by Grant-in-Aid for Scientific Research JP20K04015, JP21K13968, and JP19K14759 of the Japan Society for the Promotion of Science.

ALMA (Atacama Large Millimeter/submillimeter Array: ALMA) was manufactured by the European Southern Observatory (ESO), the National Science Foundation (NSF), and the National Institute of Natural Sciences (NINS) in Japan. It is an international astronomical observation facility operating in cooperation with. The cost of constructing and operating the ALMA telescope is paid by ESO, NSF, its collaborating organizations, the Canadian National Research Council (NRC), Taiwan’s Ministry of Science and Technology Executive Yuan (MoST), NINS and its collaborating organization, Academy Sinica (AS) and by the South Korean Science Observatory (KASI). ). The construction and operation of the ALMA telescope will be carried out by ESO on behalf of its constituent countries, the US National Astronomical Observatory in Japan, which is managed by the Association of Northeastern University of the United States (AUI), on behalf of North America, and the National Astronomical Observatory of Japan on behalf of East Asia. The Joint ALMA Observatory (JAO) aims to implement standardized implementation and management of the ALMA telescope construction, and to monitor tests and operations.

footnote. note

[1] Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Hubble Legacy Archive, a collaboration between the Space Telescope Science Institute (STScI/NASA), and the European Space Telescope Coordination Facility (ST-ECF/ESA). ) and the Canadian Astronomy Data Center (CADC/NRC/CSA).

[2] These images are described in Lupton et al. (2004), “Preparing Red-Green-Blue Images from CCD Data”, in Pacific Astronomical Society publication (DOI: 10.1086/382245). It is a tri-color composite diagram created with .