In 1926, the famous astronomer Edwin Hubble developed a morphological classification of galaxies. This method divided the galaxies into three basic groups – elliptical, spiral and lenticular. Since then, astronomers have devoted a significant amount of time and effort to find out how galaxies have been evolving for several billion years and why they acquire precisely the form that end up acquiring.
One of the most popular and widespread hypotheses on this subject is one which explains the change in the shapes of galaxies as a result of their merger, when a more compact cluster of stars held by their mutual gravity, merge together and therefore form the shape and final form of galaxies. However, according to the findings of a new study by the international group of scientists, the shape and size of the galaxies actually can influence the emergence of new stars in their Central regions.
The study was conducted under the guidance of postdoctoral fellow Ken-Ichi an Imperial official, in cooperation with the Institute for extraterrestrial physics max Planck and the National astronomical Observatory of Japan (NAOJ). To obtain a more complete picture of galactic metamorphosis the researchers conducted a series of observations of very distant galaxies.
Chart the evolution of galaxies
The study included the use of multiple telescopes, which astronomers have observed 25 galaxies located at a distance of about 11 billion light years from Earth. At that distance scientists actually observed galaxies when they were 11 billion years ago, after about 3 billion years after the Big Bang. This time is regarded by astronomers as a period of peak activity of galaxy formation in the Universe, when it formed the majority of galaxies.
“It was believed that massive elliptical galaxies formed as a result of collisions of galactic disks. However, we do not believe that all elliptical galaxies were once affected by this intergalactic event. We believe that there’s another alternative,” said an Imperial official in a press release published on the website of the Japanese astronomical Observatory.
The opportunity to catch the faint light from these distant galaxies has proved to be a complicated task and to solve it, scientists took the use of two ground and one for space telescopes. First, search for 25 galaxies, they used the 8.2-metre Subaru telescope, located in Hawaii. Then conducted surveillance of the detected objects using the Hubble space telescope and ground-based Atkarskoy a large antenna array of millimeter range (ALMA) located in Chile.
Hubble has allowed to capture the light of galaxies to determine their form (which they had 11 billion years ago), using ALMA, researchers conducted a study of submillimeter waves emitted by cold clouds of gas and dust where new stars are born. Comparing the results of both observations, astronomers were able to identify detailed picture of how these galaxy looked 11 billion years ago, when their form is still subjected to changes.
The observation of the galaxy, located 11 billion light years from us
What the researchers found, was very revealing. Image of Hubble is pointed out that in early galaxies dominated by a disk component, and not the centre bar, which we used to associate with spiral and lenticular galaxies. At the same time, the ALMA images showed that near the center of these galaxies can contain massive reservoirs of gas and dust within which there is a very active star formation.
To exclude the possibility that such active star formation could be triggered by merging of galaxies, the researchers also used to verify the data with the Very large telescope of the European southern Observatory, located in Parnasskii Observatory in Chile.
“We have received convincing evidence that dense galactic nuclei can be formed without galactic collisions. They can be formed due to the very active star formation in the center of the galaxy,” reports an Imperial official.
The results of this study may force astronomers to review current models and theories of galactic evolution, and some aspects like those, how galaxies appear lintel and spiral arms. The study also may lead to a revision of the cosmological models of evolution, not to mention the history of our own galaxy.
Who knows, maybe it will also force astronomers to revise predictions about what may happen when our milky Way galaxy and Andromeda will collide in a few billion years. The more and deeper scientists look into space, the more surprises he brings. And every time we note the observations do not correspond with our expectations, it makes scientists to reconsider the accepted hypothesis concerning the evolution of the Universe.
Astronomers figured out why galaxies have different form
Nikolai Khizhnyak