A new 'baby galaxy' offers clues about the birth of the universe

April 22, 2021
A "baby galaxy" has been found, expanding our knowledge of the cosmos. (ALMA (ESO/NAOJ/NRAO), Fujimoto et al., NASA/ESA Hubble Space Telescope)

A "baby galaxy" has been found, expanding our knowledge of the cosmos. (ALMA (ESO/NAOJ/NRAO), Fujimoto et al., NASA/ESA Hubble Space Telescope)

Researchers have uncovered a "baby galaxy" 12.9 billion light-years from Earth, whose discovery upends previous knowledge about galaxy formation in the early universe and may aid in the future identification of more hidden galaxies.

RXCJ0600-z6 is about 6,000 light-years wide, compared with the Milky Way's roughly 100,000 light-years. Astronomers have commonly believed that mini-galaxies contain chaotic movement of gases, but this one shows that they might be much calmer than initially thought. 

The researchers who discovered this diminutive galaxy described their findings in a paper published April 22 in The Astrophysical Journal

"My motivation in doing this research was, I'd like to know it's a true picture of the early universe," said lead author Seiji Fujimoto, a postdoctoral researcher of astronomy at the University of Copenhagen. "If we find a baby galaxy in the earliest universe, characterizing this galaxy's properties will direct a constraint to understand how the universe began." 

While current telescope technology can plumb the deep universe for new galaxies, it can see only those that are very bright and very large. This limitation paints a compelling but incomplete image of the universe, because these "monster-like" galaxies are quite rare, according to Fujimoto. 

To find celestial objects both small and dim, scientists may detect gravitational-lensing events that illuminate the objects. These lensing events occur when a massive celestial body pulls in light traveling around it, creating a split beam that astronomers can eventually discern on Earth. The longer it takes for one beam to follow another, the larger the gravitational lens. 

Australian researchers, for example, recently used a gravitational-lensing event to find an elusive and medium-sized black hole. And because of its small size, Fujimoto and his colleagues could detect RXCJ0600-z6 only through gravitational lensing. He and his team completed their study using data from the Atacama Large Millimeter/submillimeter Array, in Chile, as well as data from Hubble Space Telescope and the European Southern Observatory's Very Large Telescope.

Gravitational lenses can also magnify the light traveling around these celestial bodies, and in the case of RXCJ0600-z6, the light was magnified to a degree rarely observed from a galaxy so distant, according to Fujimoto. This great magnification allowed the researchers to dive into RXCJ0600-z6's internal structure, including the light frequency emitted from its gases.

Examining the mini-galaxy, Fujimoto and his colleagues discovered carbon gas, whose light frequency they eventually used to understand its movement. But the discovery of carbon gas was surprising in itself, because RXCJ0600-z6 was born only 900 million years after the Big Bang, yet the early universe contained only hydrogen and a small amount of helium, according to Fujimoto. (Even though this little galaxy sounds old, having been born almost 13 billion years ago, the image detected by Fujimoto depicts a youngster because of the length of time it takes for light to travel 12.4 billion light-years.)

Using the frequency of this carbon gas, Fujimoto could determine such movement, or kinematics, of those galactic gases. These frequencies can show how gases may be moving toward or away from Earth. With the frequencies they read, Fujimoto and his team could discern that RXCJ0600-z6 exists in a state of precocious tranquility. 

This finding surprised Fujimoto, because only older galaxies tend to show the type of ordered circulation of gases now seen in RXCJ0600-z6. One might expect that younger galaxies, seen closer to the merging of gases that created them, would harbor more random movements before they become more orderly.  

Taken together, this information can help astronomers better understand and study these infant galaxies moving forward.

NASA has selected Fujimoto's RXCJ0600-z6 for future observation by the James Webb Space Telescope, a floating infrared observatory that will launch in October. Fujimoto can already analyze the motion of cold gases, such as carbon, with the ALMA telescope, but the Webb telescope will be able to show the motion of hot gases, as well as provide images detailing star populations. 

Combining information from these advanced telescopes will allow his team to create a multilayer structure of their newfound galaxy, Fujimoto said. 

The study, "ALMA lensing cluster survey: bright [C ii] 158 µm lines from a multiply imaged sub-l* galaxy at z = 6.0719," published April 22 in Astrophysical Journal, was authored by Seiji Fujimoto, Gabriel Brammer, Vasily Kokorev, Francesco Valentino and Sune Toft, Cosmic Dawn Center and University of Copenhagen; Masamune Oguri, Yuki Yoshimura, Kotaro Kohno, Bunyo Hatsukade, Yoshiaki Ono, Kazuhiro Shimasaku, Kana Morokuma-Matsui and Kikuchihara Shotaro, The University of Tokyo; Nicolas Laporte, University of Cambridge; Jorge Gonzàlez-L´opez, Universidad Diego Portales and Carnegie Institute of Washington; Gabriel B. Caminha, University of Gronigen; Adi Zitrin, University of the Negev; Johan Richard, Centre de Recherche Astrophysique de Lyon; Masami Ouchi, National Astronomical Observatory of Japan and The University of Tokyo; Franz E. Bauer, Pontificia Universidad Catolica de Chile and Millennium Institute of Astrophysics; Ian Smail, Durham University; Hideki Umehata, RIKEN Cluster for Pioneering Research and The University of Tokyo; Daniel Schaerer, Universit´e de Gen`eve and CNRS; Kirsten Knudsen, Chalmers University of Technology; Fengwu Sun and Eiichi Egami, University of Arizona; Georgios Magdis, Cosmic Dawn Center, University of Copenhagen and Technical University of Denmark; Yiping Ao, Chinese Academy of Sciences; Miroslava Dessauges-Zavadsky and Haruka Kusakabe, Universit´e de Gen`eve; Karina Caputi, University of Groningen and Cosmic Dawn Center; Minju M. Lee, Max-Planck-Institut fur Extraterrestrische Physik; Timothy Rawle, European Space Agency; and Daniel Espada, SKA Organisation.

Correction: A previous version of this story misstated the distance of RXCJ0600-z6 from Earth. The error has been corrected.

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