Dark Matter Cradles Star Formation

It is a well known fact that galaxies can form new stars as they move through the space to join other galaxies in dense galaxy clusters which are pulled together by the powerful gravitational forces. Nevertheless, most of them tend to follow the gas filaments of dark matter that stretch between the galaxies. As they come to populate areas of space with high concentrations of matter, inevitably some galaxies will collide with others, collecting new material, which determines the triggering of a new star formation process.

The natural presumption is that galaxy clusters represent some of the best areas where galaxies can start a new star formation process. However, the Spitzer Space Telescope has shown that the dark matter filaments can provide with more fertile material than that resulted in the outcome of a galactic collision.

The idea was first proposed back in the 1990s by a couple of researchers who argued that the relatively small speeds between galaxies and the gas filaments would favor galaxies to stay more time apart from each other in order to trigger star formation processes by creating gravitational disruptions inside them. By studying the brightness of starburst galaxies in the Abell 1763 galaxy cluster in the 24 micron wavelength, the Spitzer Space Telescope was able to determine that, in fact, there are more such galaxies sweeping gas from the filaments than in some of the densest areas of the cluster.

A rough estimation shows that the Abell 1763 galaxy cluster, located 42 million years away from Earth, presents a ratio of 2:1 between the starburst galaxies in the gas filaments and those in the central regions of the cluster. John Hibbard from the National Radio Astronomy Observatory explains that galaxies form more stars in the gas filaments because they actually spend more time accumulating material from them than the time spent during a galactic collision. Furthermore, it seems that galaxies surrounding the central regions of the clusters lose relatively quickly most of their gas, disabling the star formation process.

Our galaxy is part of the Local Group, which is not by any means a galaxy cluster, but it may also start a new star formation process somewhere in the next 3 billion years, when it will probably collide and merge with its sister galaxy Andromeda.