Using Atacama’s Large Millimeter / submillimeter Array (ALMA), astronomers found a spinning baby galaxy 1 / 100th the size of the Milky Way at a time when the Universe only had seven percent of its size. current age. Thanks to the help of the gravitational lensing effect, the team was able to explore for the first time the nature of the small and dark “normal galaxies” of the beginning of the Universe, representative of the main population of the first galaxies. which greatly advances our understanding of the initial phase of the evolution of the galaxy.
“Many of the galaxies that existed at the beginning of the Universe were so small that their luminosity is far below the limit of today’s largest telescopes on Earth and in space, making it difficult to study their properties and their internal structure, ”explains Nicolas Laporte, a Kavli Senior Fellow at the University of Cambridge. “However, the light coming from the galaxy named RXCJ0600-z6, was strongly amplified by the gravitational lens, making it an ideal target for studying the properties and structure of a typical baby galaxy.”
Gravitational lensing is a natural phenomenon in which light emitted from a distant object is bent by the gravity of a massive body such as a galaxy or a cluster of galaxies in the foreground. The name “gravitational lens” is derived from the fact that the gravity of the massive object acts like a lens. When we look through a gravitational lens, the light from distant objects is intensified and their shapes are stretched. In other words, it is 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. By combining the power of ALMA, with the help of natural telescopes, researchers are able to discover and study paler galaxies.
Why is it crucial to explore the weakest galaxies at the beginning of the Universe? Theory and simulations predict that the majority of galaxies formed a few hundred million years after the Big Bang are small and therefore weak. Although several galaxies of the first Universe have already been observed, those studied were limited to the most massive objects, and therefore to the least representative galaxies, at the beginning of the Universe, due to the capacities of telescopes. The only way to understand the standard formation of the first galaxies and to get a complete picture of the formation of galaxies is to focus on the weakest and most numerous galaxies.
The ALCS team performed a large-scale observing program that took 95 hours, which is a very long time for ALMA observations, to observe central regions of 33 galaxy clusters that could cause a gravitational lens. 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 affected by the gravitational lens created by this natural telescope. ALMA detected the light of carbon ions and stardust in the galaxy and, with data taken with the Gemini 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 this data suggests that part of this source is seen 160 times brighter than it inherently is.
By precisely 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. By combining data from the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope with a theoretical model, the team succeeded in reconstructing the real shape of the distant galaxy RXCJ0600-z6. The total mass of this galaxy is about 2-3 billion times that of the Sun, or about 1 / 100th the size of our own Milky Way.
What amazed the team was that the RXCJ0600-z6 is running. Traditionally, gas in young galaxies was thought to have random and chaotic motion. It was only recently that ALMA discovered several young spinning galaxies that challenged the traditional theoretical framework, but these were several orders of magnitude brighter (larger) than RXCJ0600-z6.
“Our study demonstrates, for the first time, that we can directly measure the internal motion of these weak (less massive) galaxies in the early Universe and compare it with theoretical predictions,” says Kotaro Kohno, professor at the University of Tokyo. and the ALCS team leader.
“The fact that the RXCJ0600-z6 has a very high magnification factor also raises expectations for future research,” says Seiji Fujimoto, DAWN member of the Niels Bohr Institute. “This galaxy has been selected, out of hundreds, for observation by the James Webb Space Telescope (JWST), the next-generation space telescope to be launched this fall. Through joint observations using ALMA and JWST, we will unveil the properties gas and stars in a small galaxy and its internal motions. When the Thirty Meter Telescope and the Extremely Large Telescope are completed, they may be able to detect star clusters in the galaxy and perhaps even solve problems. individual stars. There is an example of a gravitational lens that was used to observe a single star 9.5 billion light years away, and this research has the potential to extend it to less than a billion years later. the birth of the Universe. “