New evidence of dark matter around small galaxies

NASA's Hubble Space Telescope has just discovered a new convincing evidence that galaxies are surrounded by dark matter halo.

Observing the vibrant center of the galaxy cluster Perseus, the Hubble telescope detects large populations including small galaxies that remain intact while larger galaxies lying around them are torn apart by drag. from the neighbor galaxy. The results were published in the March 1 issue, the Monthly Notices of the Royal Astronomical Society.

Dark matter is an invisible form of matter that accounts for most of the universe's mass. Astronomers have concluded the existence of dark matter by observing its gravitational pull on ordinary matter including stars, gas and dust.

The images taken by Hubble telescope provided additional evidence that untangled galaxies are surrounded by a curtain of dark matter. It was this curtain that protected them from rude neighbors. Astronomer Christopher Conselice of the University of Nottingham and the director of Hubble's observations said: 'We were surprised to find that there are many dwarf galaxies located in the center of the cluster that look very round, peaceful, they do not have any traces of harassment. These dwarf galaxies are very old and exist in the galaxy cluster long ago. So if any phenomenon disturbs them, it must happen at this time. Certainly dark matter has dominated those galaxies. '

Dwarf galaxies may contain more dark matter than spiral galaxies. Conselice said: 'With this result, we cannot say exactly whether the mass of dark matter in dwarf galaxies is greater than the mass of dark matter in the Milky Way galaxy. Despite the fact that spiral galaxies have been destroyed, while dwarf galaxies are not. That suggests that the above statement may be true '.

Above are the four dwarf galaxies located in the vibrant center of the galaxy cluster Perseus. They look soft and symmetrical, indicating that they are not disturbed by the gravitational pull from the dense environment. However, larger galaxies around it are torn by traction from other galaxies. (Photo: NASA, ESA, C. Conselice and S. Penny (University of Nottingham))

First mentioned since 80 years ago , dark matter is thought to be the glue that binds galaxies together. Astronomers believe that dark matter forms a vital framework for the universe, forming the flank for the formation of galaxies thanks to gravity. Earlier studies using the Hubble telescope and the Chandra X-ray Observatory (NASA) also found evidence of dark matter in clusters of galaxies called Bullet Clusters. Hubble's new observation continues to search for dark matter in single galaxies.

Hubble's state-of-the-art surveillance camera has entered the view of 29 elliptical dwarf galaxies in the Perseus cluster located 250 million light-years away, which is also one of the closest galaxy clusters to Earth. Among them are 17 new galaxies.

Because dark matter cannot be observed, astronomers identify it through indirect evidence. The most common method is to determine the velocity of stars or groups of stars as they move randomly in the galaxy or as they orbit around the galaxy. The Perseus cluster is too far away from telescopes, making it difficult to observe individual stars as well as to determine their movements. Therefore Conselice and his team created a new technique to detect dark matter in dwarf galaxies by determining the minimum mass that dwarf galaxies must achieve in order to protect it from being destroyed. tangled by gravitational forces from larger galaxies.

A detailed study of the aforementioned small galaxies is possible with the help of Hubble's modern camera. Conselice and his team first discovered them with the WIYN telescope located at Kitt National Observatory outside Tucson, Arizona. These observations suggest that most galaxies exist in a peaceful state, hence the dominance of dark matter. Conselice said: 'Observations conducted on the ground cannot be ascertained, so we need Hubble telescope images.'

Other members of the research team include Samantha J. Penny of Nottingham University, Sven De Rijcke of Ghent University in Belgium, and Enrico Held of the University of Padua in Italy.

Refer:
Penny et al.Hubble Space Telescope survey of the Perseus Cluster - I. The structure and dark matter content of the dwarf spheroidals cluster.Monthly Notices of the Royal Astronomical Society, 2009;393 (3): 1054 DOI: 10.1111 / j.1365-2966.2008.14269.x