The spiral galaxies such as our Milky Way are produced of a star disc and gas. The quantity of revolutions abnormally rapidly of these discs indicates that the total mass of the spiral galaxies is fairly larger than the visible star and gas mass: the galaxies include great quantities of hidden matter, called “black”, from which precise nature escapes nevertheless these days the physicists, but who according to traditional cosmological scenarios’ would reside in a wide spheroid halation, rather than in the discs. The forces brought into play at the time of the collisions of galaxies tear off great quantities of gas and stars with their discs and project them in the intergalactic medium in the shape of filaments or matter rings.
An international group carried out within Laboratory AIM by researchers of the ECA (3) and CNRS studied the remains of collision of a galaxy, NGC5291, using observations radios obtained with Broad Really Array (four) and of a digital model of the formation of this method. According to their simulations carried out on the supercomputers CEA/CCRt (five), NGC5291 was a traditional spiral galaxy when it was victim of a violent collision, 360 million years ago. The impact would have formed a gigantic gas ring which nowadays extends on almost 500.000 light-years, and which was parcelled out in numerous condensations.
The researchers highlighted in many of these condensations abnormally high speeds of gas, attesting of a total mass 3 times higher than the visible mass in the form of gas or of stars. These remains of collision thus include significant quantities of black matter. This result published by the evaluation Science, is especially unexpected. Indeed, the black matter initially present in the halations about the galactic discs need to be characterized by disordered quickly movements which make them insensitive with the forces which are exerted at the time of the shocks in between galaxies. And hence the hidden mass detected in the remains of these collisions can come only from the discs of the spiral galaxies.
These benefits straight do not reveal the nature of this mysterious constituting. Nonetheless, amongst the candidates, most all-natural would be really cold molecular hydrogen, detectable with significantly difficulty contrary to traditional interstellar gas. They are thus numerous tens of pourcents mass of the discs of the spiral galaxies which would be concealed with the observations, in addition to the mass currently hidden in the halations.