Tag Archives: galaxy formation

New data challenges consensus on galaxy formation

The uncertainty of science: A new study has found that the accepted consensus for the formation of large elliptical galaxies does not work, and that, rather than forming from the merger of smaller spiral galaxies, ellipticals formed in place from the material at hand.

From the press release [pdf].

“We started from the data, available in complete form only for the closer galaxies and in incomplete form for the more distant ones, and we filled the ‘gaps’ by interpreting and extending the data based on a scenario we devised” comments Mancuso. The analysis also took into account the phenomenon of gravitational lensing, which allows us to observe very distant galaxies belonging to ancient cosmic epochs.

In this “direct” manner (i.e., model-independent) the SISSA group obtained an image of the evolution of galaxies even in very ancient epochs (close, in a cosmic timescale, to the epoch of reionization). This reconstruction demonstrates that elliptical galaxies cannot have formed through the merging of other galaxies, “simply because there wasn’t enough time to accumulate the large quantity of stars seen in these galaxies through these processes”, comments Mancuso. “This means that the formation of elliptical galaxies occurs through internal, in situ processes of star formation.

The important take-away of this result is that it shows that the present theory of galaxy formation, where smaller spiral galaxies merge to form larger elliptical galaxies, does not fit the data. And if a theory does not fit the data, it must be abandoned.

Telescope teamwork produces spectacular galaxy image

M106

Combining images from a host of space and ground-based telescopes, astronomers have created a spectacular image of the galaxy M106.

This galactic fireworks display is taking place in NGC 4258 (also known as M106), a spiral galaxy like the Milky Way. This galaxy is famous, however, for something that our Galaxy doesn’t have – two extra spiral arms that glow in X-ray, optical, and radio light. These features, or anomalous arms, are not aligned with the plane of the galaxy, but instead intersect with it.

The anomalous arms are seen in this new composite image of NGC 4258, where X-rays from NASA’s Chandra X-ray Observatory are blue, radio data from the NSF’s Karl Jansky Very Large Array are purple, optical data from NASA’s Hubble Space Telescope are yellow and blue, and infrared data from NASA’s Spitzer Space Telescope are red.

A new study of these anomalous arms made with Spitzer shows that shock waves, similar to sonic booms from supersonic planes, are heating large amounts of gas – equivalent to about 10 million Suns. What is generating these shock waves? Radio data shows that the supermassive black hole at the center of NGC 4258 is producing powerful jets of high-energy particles. Researchers thinkthat these jets strike the disk of the galaxy and generate shock waves. These shock waves, in turn, heat some of the gas – composed mainly of hydrogen molecules – to thousands of degrees.

The astronomers also used the Herschel Space Observatory to confirm the data from Spitzer.

A trio of supermassive black holes

Astronomers have discovered a trinary of supermassive black holes at the center of a distant collision of multiple galaxies.

Astronomer Roger Deane of the University of Cape Town in South Africa and his colleagues have been watching a particular quasar, known as SDSS J1502+1115, in the constellation Boötes. Other astronomers had found that the object, located 4.3 billion light-years from Earth, possessed two supermassive black holes, each the center of a large galaxy smashing into another. The black holes are at least 24,000 light-years apart.

Deane wanted to confirm their existence, so he used an intercontinental array of radio dishes that yields even sharper views than the Hubble Space Telescope. Lo and behold, one of the black holes turned out to be two. “We were incredibly surprised,” says Deane, whose team reports its findings online today in Nature.

While the discovery of this system is incredibly cool, this article in the journal Science is surprisingly incorrect on some points, while also missing the main story.
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Astronomers have discovered that a large number of dwarf galaxies are orbiting Andromedea in a flat plane, like our solar system, contrary to all predictions.

The uncertainty of science: Astronomers have discovered that a large number of dwarf galaxies are orbiting Andromedea in a flat plane, like our solar system, contrary to all predictions.

The study reveals almost 30 dwarf galaxies orbiting the larger Andromeda galaxy in this regular, solar system-like plane. The astronomers’ expectations were that these smaller galaxies should be buzzing around randomly, like bees around a hive. “This was completely unexpected,” said Geraint Lewis, one of the lead authors on the Nature publication. “The chance of this happening randomly is next to nothing.” The fact that astronomers now see that a majority of these little systems in fact contrive to map out an immensely large – approximately one million light years across – but extremely flattened structure, implies that this understanding is grossly incorrect. Either something about how these galaxies formed, or subsequently evolved, must have led them to trace out this peculiar, coherent, structure.