Theoretical predictions have been confirmed with the discovery of an outflow of molecular gas from a quasar when the Universe was less than a billion years old. The results obtained from the observations of the ALMA telescope are of great importance for understanding the processes of star formation in galaxies. Dr. Darko Donevski from the NCBJ Astrophysics Division participated in the work of the research team.

Joint Release by Hokkaido University, University of Tsukuba, Waseda University, the National Astronomical Observatory of Japan and the National Centre for Nuclear Research (NCBJ) Poland.

A quasar is a compact region powered by a supermassive black hole located in the center of a massive galaxy. They are extremely luminous, with a point-like appearance similar to stars, and are extremely distant from Earth. Owing to their distance and brightness, they provide a peek into conditions of the early Universe, when it was less than 1 billion years old.

A team of researchers led by Assistant Professor Dragan Salak at Hokkaido University, Assistant Professor Takuya Hashimoto at the University of Tsukuba, and Professor Akio Inoue at Waseda University, has discovered the first evidence of suppression of star formation driven by an outflow of molecular gas in a quasar-host galaxy in the early Universe. Their findings, based on observations they made using the Atacama Large Millimeter/submillimeter Array (ALMA), in Chile, were published in The Astrophysical Journal.

Molecular gas is vital to the formation of stars. As the primary fuel of star formation, the ubiquity and high concentrations of molecular gas within a galaxy would lead to a vast number of stars being formed. By ejecting this gas into intergalactic space faster than it could be consumed by star formation, molecular outflows effectively suppress the formation of stars in galaxies that host quasars.

“Theoretical work suggests that molecular gas outflows play an important role in the formation and evolution of galaxies from an early age, because they can regulate star formation,” Salak explains. “Quasars are especially energetic sources, so we expected that they may be able to generate powerful outflows.”

The quasar the researchers observed, J2054-0005, has a very high redshift—it and the Earth are apparently moving away from each other very fast. “J2054-0005 is one of the brightest quasars in the distant Universe, so we decided to target this object as an excellent candidate to study powerful outflows,” Hashimoto says. The researchers used ALMA to observe the outflow of molecular gas from the quasar. As the only telescope in the world that has the sensitivity and frequency coverage to detect molecular gas outflows in the early Universe, ALMA was key to this study.

Speaking about the method used in the study, Salak comments: “The outflowing molecular (OH) gas was discovered in absorption. This means we did not observe microwave radiation coming directly from the OH molecules; instead, we observed the radiation coming from the bright quasar—and absorption means that OH molecules happened to absorb a part of the radiation from the quasar. So, it was like revealing the presence of a gas by seeing the ‘shadow’ it cast in front of the light source.” The findings from this study are the first strong evidence that powerful molecular gas outflows from quasar-host galaxies exist and impact galaxy evolution at the early cosmic age. “Molecular gas is a very important constituent of galaxies because it is the fuel for star formation,” Salak concludes. “Our findings show that quasars are capable of suppressing star formation in their host galaxies by ejecting molecular gas into intergalactic space.”

Supplementary Information

The involvement of NCBJ scientists in the discovery

Dr Darko Donevski, an assistant professor at the Astrophysics Division at the National Centre for Nuclear Research, participated in the work of the international research team. Dr. Donevski, who is a grant holder of the National Science Centre (NCN), participated in the observations and data analysis obtained with the ALMA interferometer, which is one of the most powerful, ground-based astronomical instruments. Dr. Donevski applied the method called “spectral modeling” and found it likely that the center of an observed distant galaxy harbors a supermassive black hole. Future follow-up observations with space telescopes will confirm or rule out this prediction. This was the first time that researchers from the NCBJ participated in the discoveries of massive dusty quasars that were formed in the first billion years of cosmic history. In this regard, the discovery opened up new possibilities for research in which NCBJ will be involved in the coming years.

Original article

Dragan Salak, et al. Molecular outflow in the reionization-epoch quasar J2054-0005 revealed by OH 119 μm observations. The Astrophysical Journal. February 1, 2024. DOI: 10.3847/1538-4357/ad0df5

Funding

This study was supported by the ALMA Japan Research Grant of National Astronomical Observatory of Japan (NAOJ) Atacama Large Millimeter/submillimeter Array (ALMA) Project (NAOJ-ALMA-294, NAOJ-ALMA-2018-09B); Leading Initiative for Excellent Young Researchers, Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT; HJH02007); Japan Society for the Promotion of Science (JSPS) KAKENHI (22H01258, 7H06130, 20H01951, 22H0493); National Science Center (NCN) SONATA (UMO-2020/39/D/ST9/00720); and the Japan Science and Technology Agency (JST) SPRING (JPMJSP2119).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.