Most Distant Dwarf Galaxy Detected

[n2doc]

ScienceDaily (Jan. 18, 2012) — Scientists have long struggled to detect the dim dwarf galaxies that orbit our own galaxy. So it came as a surprise on Jan. 18 when a team of astronomers using Keck II telescope's adaptive optics has announced the discovery of a dwarf galaxy halfway across the universe.

The new dwarf galaxy found by MIT's Dr. Simona Vegetti and colleagues is a satellite of an elliptical galaxy almost 10 billion light-years away from Earth. The team detected it by studying how the massive elliptical galaxy, called JVAS B1938 + 666, serves as a gravitational lens for light from an even more distant galaxy directly behind it. Their discovery was published in the Jan. 18 online edition of the journal Nature.

Like all supermassive elliptical galaxies, JVAS B1938 + 666's gravity can deflect light passing by it. Often the light from a background galaxy gets deformed into an arc around the lens galaxy, and sometimes what's called an Einstein ring. In this case, the ring is formed mainly by two lensed images of the background galaxy. The size, shape and brightness of the Einstein ring depends on the distribution of mass throughout the foreground lensing galaxy.

Vegetti and her team obtained extra sharp near-infrared image of JVAS B1938 + 666 by using the 10-meter Keck II telescope and its adaptive optics system, which corrects for the blurring effects of Earth's atmosphere, and provides stunningly sharp images. With these data, they neatly determined the mass distribution of JVAS B1938 + 666 as well as the shape and brightness of the background galaxy.

more
http://www.sciencedaily.com/releases/2012/01/120118165143.htm

[eppur_se_muova]

1. BBC chose to headline the dark matter aspect ...

Dark matter galaxy hints seen 10bn light-years away (BBC)

Astronomers have spotted a "dwarf" galaxy some 10 billion light-years away which may be made mostly of the mysterious material called dark matter.

The dwarf was found using a technique called gravitational lensing. It is only the second dark dwarf ever seen, and it is by far the most distant.

The fact that so few dwarf galaxies are seen in our own cosmic neighbourhood has remained a conundrum in astronomy.

The study in Nature could explain it: they may be overwhelmingly dark matter.

Dwarf galaxies often occur in the periphery of larger galaxies, where they are known as satellites - the Milky Way may have many as well.
***
more: http://www.bbc.co.uk/news/science-environment-16610153