Friday, February 27, 2015

La relazione tra materia oscura, galassie e buchi neri

According to a new study recently published in The Astrophysical Journal, the invisible hand of dark matter would also affect the growth of black holes. The fact is that it is believed that every galaxy has a supermassive black hole at its center, with a mass that is even billions of times that of the Sun, and the heavier the galaxy, the bigger the black hole. The question that scientists have been asking for a long time is whether this fact is related and in what way with dark matter, that big slice of matter that makes up our universe and that we can not observe because it does not emit electromagnetic radiation.

Well, thanks to this new research, conducted by a group of researchers from the Harvard-Smithsonian Center for Astrophysics (Cfa) on a large group of elliptical galaxies, It seems we have been able to demonstrate that dark matter plays a central role in the evolution of these black holes.
This new research was designed to solve a controversy opened by earlier studies. Some of them had identified a relationship between the mass of the black hole at the center of the galaxy and the total mass of the stars in it, while more recent observations suggested a close correlation between this overall stellar mass and dark matter. Each galaxy is surrounded by a halo of dark matter that can weigh as much as a trillion suns and extends for hundreds of thousands of light years. What was not clear was which of these relations was the dominant one.

It was therefore a question of studying specifically the link between the halo of dark matter surrounding galaxies and supermassive black holes. To do this, Ákos Bogdán and Andy D. Goulding, the latter stationed in Princeton, studied more than 3,000 elliptical galaxies, using the motions of stars to "weigh" black holes in the center of galaxies. Well, the answer was clear: it is the relationship between the mass of dark matter and the mass of the black hole that is dominant, representing a stronger relationship than that between a black hole and the mass of stars in the galaxy.

All of this is also probably related, according to the study, to how elliptical ligands evolve. The latter form when two smaller galaxies merge, mixing stars and dark matter together. Because dark matter is much larger, it shapes the galaxy in formation, leading to the growth of the central black hole.

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