Cosmic giants against dwarf galaxies

A recent study reports the results of an observational campaign conducted on over 20,000 galaxies and shows that the rate of star formation as a result of a collision depends on the size of the galaxy compared to that with which it is colliding. The article can be found in the Monthly Notices of the Royal Astronomical Society.
When two galaxies collide different sizes, the larger galaxy prevents the smaller of generating new stars, according to says a study of more than 20,000 galaxies interacting. The research, published in the journal Monthly Notices of the Royal Astronomical Society, also showed that when two galaxies collide are of similar size, both begin to produce stars at a much more rapid rate.


Credit: ICRAR

Astrophysicist Luke Davies, of the University of Western Australia, which is part of the International Centre for Radio Astronomy Research (ICRAR), said that our biggest neighbor, Andromeda, is racing on a collision course with the Milky Way in about 400,000 kilometers per hour. “Not to worry, for now, the two galaxies will collide for 4 billion years or so,” says Davies. “But to continue studying these cosmic collisions allows us to better understand how galaxies grow and evolve.”
In the past, astronomers believed that the clash between two galaxies would cause the setting in motion of their gas clouds, triggering therefore the birth of new stars. The study led by Davies and conducted using data from the observational campaign Galaxy and Mass Assembly (GAMA), made with the Anglo-Australian telescope placed in the region of New South Wales, however, shows that this model is too simplistic.
The collected data indicate that the increase in the rate of star formation following a collision, or the formation of new stars same, depends on the size of the galaxy compared to that with which it is colliding.
“When two galaxies of similar mass collide, both increase its rate of star formation,” says Davies. “When instead one of the two galaxies significantly exceeds the other in size, we have found that the star formation process change for both, just in different ways. The most massive galaxy begins to form new stars rapidly, while the smaller galaxy suddenly is struggling to form.”
“This could be because of the larger galaxy rips gas of his little companion, leaving it with no fuel for the formation of new stars, or it prevents the smaller galaxy to get the extra gas it needs.”
So what will happen in four billion years the Milky Way and Andromeda? Davies says that these two galaxies are like “cosmic tanks”, both relatively large and with similar masses. “The more they come near to each other, most will begin to influence each other’s processes of star formation, and will continue to do so until they merge to become a new galaxy, which some already call ‘Milkomeda’.

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