ALMA discovers a rotating children’s galaxy with the help of a natural space telescope

The galaxy cluster RXCJ0600-2007 taken from the NASA / ESA Hubble Space Telescope, combined with gravitational lensing images of the distant galaxy RXCJ0600-z6, 12.4 billion light-years away, observed by ALMA (shown in red). Due to the effect of gravitational lensing by the galactic cluster, the image of RXCJ0600-z6 intensified and enlarged, and appeared to be divided into three or more parts. Credit: ALMA (ESO / NAOJ / NRAO), Fujimoto ka, Hubble Space Telescope NASA / ESA

Using the Atacama Large Millimeter / submillimeter Array (ALMA), astronomers found a rotating baby galaxy 1/100 of the size of the at a time when the universe was only 7 percent of its current age. Thanks to the help of the effect of a gravitational lens, the team was able to explore for the first time the nature of small and dark “normal galaxies” in the early universe, representative of the main population of the first galaxies, which greatly advances our understanding of the initial phase of galactic evolution.

“Many of the galaxies that existed in the early universe were so small that their brightness is far below the limit of today’s largest telescopes on Earth and in Space, making it difficult to study their features and internal structure,” says Nicolas Laporte, Kavli. Senior Fellow at the University of Cambridge. “However, the light coming from the galaxy called RXCJ0600-z6, has been greatly magnified by gravitational lensing, making it an ideal target for studying the properties and structure of typical baby galaxies.”

Gravitational lensing is a natural phenomenon in which light emitted by a distant object is bent by the gravity of a massive body such as a galaxy or galactic cluster located in the foreground. The name “gravitational lensing” comes from the fact that the gravity of the mass object acts as a lens. When we look through a gravitational lens, the light from distant objects intensifies and their shapes are extended. In other words, it’s a “natural telescope” floating in space.

The ALMA Lensing Cluster Survey (ALCS) team used ALMA to search for a large number of galaxies in the early universe that are magnified by gravitational lensing. Combining the power of ALMA, with the help of natural telescopes, the researchers are able to discover and study weaker galaxies.

Why is it important to explore the weakest galaxies in the early universe? Theory and simulations predict that most galaxies formed several hundred million years after the Big Bang are small, and thus weak. Although several galaxies in the early universe had previously been observed, those studied were limited to the most massive objects, and therefore the least representative galaxies in the early universe, due to telescopic capabilities. The only way to understand the standard formation of the first galaxies, and get a complete picture of galaxy formation, is to focus on the weaker and more numerous galaxies.

The ALCS team performed a large-scale observation program that lasted 95 hours, which is a very long time for ALMA observation, to observe the central regions of 33 galactic clusters that could cause gravitational lensing. One of these clusters, called RXCJ0600-2007, is located in the direction of the constellation Lepus, and has a mass 1000 trillion times that of the Sun. The team discovered a single distant galaxy that is hit by the gravitational lens created by this natural telescope. ALMA detected the light of carbon ions and stellar dust in the galaxy, and together with data taken by the Twin Telescope, determined that the galaxy is seen as it was about 900 million years after the Big Bang (12.9 billion years ago). ). Further analysis of these data suggested that part of this source is seen 160 times brighter than it is inside.

By accurately measuring the mass distribution of the galaxy cluster, it is possible to “undo” the gravitational lensing effect and restore the original appearance of the magnified object. Combining data from the Hubble Space Telescope and a Very Large Telescope from the European Southern Observatory with a theoretical model, the team managed to reconstruct the effective shape of the distant galaxy RXCJ0600-z6. The total mass of this galaxy is about 2 to 3 billion times that of the Sun, which is about 1/100 of the size of our own Milky Way Galaxy.

What amazed the team was that RXCJ0600-z6 rotates. Traditionally, gas in young galaxies has been thought to have random chaotic motion. Only recently has ALMA discovered several rotating young galaxies that have challenged the traditional theoretical framework, but these have been several sizes brighter (larger) than RXCJ0600-z6.

“Our study shows, for the first time, that we can directly measure the internal motion of such weak (less massive) galaxies in the early Universe and compare it with the theoretical predictions,” says Kotaro Kohno, a professor at the University of Tokyo. and the leader of the ALCS team.

“The fact that RXCJ0600-z6 has a very high magnification factor also raises expectations for future research,” explains Seiji Fujimoto, a DAWN fellow at the Niels Bohr Institute. “This galaxy has been selected, among hundreds, to be observed by the James Webb Space Telescope (JWST), the next generation space telescope launched this fall. Through joint observations using ALMA and JWST, we will reveal the properties of gas and stars in a baby. galaxy and its internal motions When the Thirty Metric Telescope and the Extremely Large Telescope are completed, they may be able to detect clusters of stars in the galaxy, and may even dissolve single stars, an example of gravitational lensing that was used to observe one star at 9 p.m. , 5 billion light-years away, and this research can extend this to less than a billion years after the birth of the Universe. “

These observational results have been presented in Seiji Fujimoto and others. “ALMA Lensing Cluster Survey: Brilliant [CII] 158 μm Lines of Multilayered Sub-L * Galaxy at z = 6.0719 “in the Astrophysics Journal April 22, 2021, and Nicolas Laporte and others. “ALMA Lensing Cluster Survey: strongly lensed multiple imaged dust system at z> 6” in the Monthly Notices of the Royal Astronomical Society on April 22, 2021.

Hubble watches cosmic light flex

Additional information:
S. Fujimoto et al. ALMA Lensing Cluster Survey: Brilliant [CII] 158 μm Lines of Multilayered Sub-L Galaxy at z = 6.0719, Astrophysics Journal, DOI: 10.3847 / 1538-4357 / abd7ecs

N. Laporte et al. ALMA Lensing Cluster Survey: strongly lensed multiple imaged dust system at z ≥6, Monthly Notices of the Royal Astronomical Society (2021). DOI: 10.1093 / mnras / stab191

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