Tuesday, October 16, 2012

When galaxies eat galaxy

Using gravitational lensing, Astronomers University of Utah (USA) found that the center of massive galaxies will ultimately become denser than normal galaxies.

"We found that over the past 6 billion years matter making massive elliptical galaxies, gaining a greater concentration in their centers. This is evidence that large galaxies collide with each other in order to create an even greater - says astronomer Adam Bolton, Lead author of the work.

- The previous work was focused on the fact that massive galaxies grow in the first place, "eating" a lot of small ones. And we believe that the collision between the massive galaxies is just as important as the small "snacks".

Results of the study are based on observations with the 2.5-meter optical telescope Apache Point Observatory and space-based telescope data “Hubble ". With these tools were analyzed 79 gravitational lenses - Galaxies that lie between Earth and a more distant galaxies, which, in fact, been the subject of research. The strength and intensity of the lensing mass astronomers to accurately set the galaxies themselves, "lens" - a massive elliptical formations containing hundreds of billions of stars each.

"They are the end product of collisions and mergers of galaxies of previous generations - perhaps hundreds of such encounters" - emphasizes Adam Bolton.

This technique allowed us not only to refine the total mass of galaxies, "lens", but also to clarify the distribution of matter within them. That mass distribution shows that elliptical galaxies have evolved not so much by way of absorption of small galaxies (like the Milky Way, crushes under her neighboring dwarf formation), as in the merger of giants with giants. And the image in the end supergiant can be hundreds of times more massive than the same Milky Way.

The fact is that when a large galaxy absorbs small, it "sucks" from the last gas and the stars of the "lesser brothers" remain on the periphery of the new entity. But if the face of the galaxy of comparable size, their structures begin profound interpenetration. A substantial part of the stars is paving the way to the center of the resulting galaxy. That is a high density of light at the center says it is part of the interaction of this - a deep, penetrating character typical collision of equal mass objects.

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