Subaru: Surprising Discovery of Rare 'Emerald-Cut' Galaxy

[bystander]

Surprising Discovery of Rare 'Emerald-Cut' Galaxy
Subaru Telescope | NAOJ | 2012 Mar 19

[i]False-color image of LEDA 074886 taken with Subaru Telescope's Suprime-Cam. The central contrast has been adjusted to reveal the inner disk/bar-like component. (Credit: L. Spitler (Swinburne University of Technology, Australia)[/i]

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An international team of astronomers—from Australia, Germany, Switzerland, and Finland—has discovered a rare, rectangular-shaped galaxy (LEDA 074886) that has a striking resemblance to an emerald-cut diamond. While using the Subaru Prime Focus Camera (Suprime-Cam) to look for globular clusters of stars swarming around NGC 1407, a bright, giant galaxy in the Constellation Eridanus and 70 million light years from Earth, the researchers discovered an unusually shaped dwarf galaxy toward the edge of their image. Professor Alister Graham (Swinburne University of Technology, Australia), lead author of the paper describing the research, said, "It's one of those things that just makes you smile because it shouldn't exist, or rather, you don't expect it to exist." Its discovery allows astronomers to obtain useful information for modeling other galaxies.

Most galaxies in the universe around us exist in one of three forms: ellipsoidal, disk-like (usually in the shape of a flattened circular disk hosting a spiral pattern of stars), or irregular. Dwarf galaxies, probably the most common galaxies in the Universe, are small and have low intrinsic brightness (i.e., luminosity). One of the reasons that LEDA 074886 was hard to find is its dwarf-like status; it has 50 times less stars than our own Milky Way Galaxy, and its distance from Earth is equivalent to that spanned by 700 Milky Way galaxies placed end-to-end. The combined advantages of Subaru's large 8.2m primary mirror and its camera at prime focus gave the researchers such a wide field of view that they could observe objects beyond their intended targets and make the surprising discovery of the emerald-shaped dwarf galaxy. Additional information gleaned from the use of green, red, and infrared filters along with the good image quality seeing in the observation enabled the researchers to see and measure a stellar disk embedded within the rectangular-shaped galaxy. The blue color of the inner disk suggested a younger average age for this stellar population.

The astronomers suspect that the emerald-cut galaxy may resemble an inflated disk seen side-on, like a short cylinder. Research co-author Professor Duncan Forbes (Swinburne University of Technology, Australia) explained, "One possibility is that the galaxy may have formed out of the collision of two spiral galaxies. While the pre-existing stars from the initial galaxies were strewn to large orbits creating the emerald-cut shape, the gas sank to the mid-plane where it condensed to form new stars and the disk that we have observed."

Despite its apparent uniqueness, partly due to its chance orientation, the team has gathered useful information for modeling other galaxies. While the outer rectangular shape is somewhat like galaxy simulations that don't involve the production of new stars, the disk-like structure is comparable with simulations involving star formation. "This highlights the importance of combining lessons learned from both types of past simulations, for better understanding of galaxy evolution," says Professor Graham. When our own disk-shaped Milky Way Galaxy collides with the disk-shaped Andromeda Galaxy in about three billion years from now, we may become inhabitants of a rectangular looking galaxy.

Astronomers discover 'emerald-cut' galaxy
Swinburne University of Technology | 2012 Mar 20

[i]LEDA 074886: a dwarf galaxy with a curious rectangular shape. (Credit: Swinburne University of Technology)[/i]

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An international team of astronomers has discovered a rare square galaxy with a striking resemblance to an emerald cut diamond.

The astronomers - from Australia, Germany, Switzerland and Finland - discovered the rectangular shaped galaxy within a group of 250 galaxies some 70 million light years away.

"In the Universe around us, most galaxies exist in one of three forms: spheroidal, disc-like, or lumpy and irregular in appearance," said Associate Professor Alister Graham from Swinburne University of Technology

He said the rare rectangular-shaped galaxy was a very unusual object. "It's one of those things that just makes you smile because it shouldn't exist, or rather you don't expect it to exist.

"It's a little like the precarious Leaning Tower of Pisa or the discovery of some exotic new species which at first glance appears to defy the laws of nature."

The unusually shaped galaxy was detected in a wide field-of-view image taken with the Japanese Subaru Telescope for an unrelated program by Swinburne astrophysicist Dr Lee Spitler.

The astronomers suspect it is unlikely that this galaxy is shaped like a cube. Instead, they believe that it may resemble an inflated disc seen side on, like a short cylinder.

Support for this scenario comes from observations with the giant Keck Telescope in Hawaii, which revealed a rapidly spinning, thin disc with a side on orientation lurking at the centre of the galaxy. The outermost measured edge of this galactic disc is rotating at a speed in excess of 100,000 kilometres per hour.

"One possibility is that the galaxy may have formed out of the collision of two spiral galaxies," said Swinburne's Professor Duncan Forbes, co author of the research.

"While the pre-existing stars from the initial galaxies were strewn to large orbits creating the emerald cut shape, the gas sank to the mid plane where it condensed to form new stars and the disc that we have observed."

Despite its apparent uniqueness, partly due to its chance orientation, the astronomers have managed to glean useful information for modelling other galaxies.

While the outer boxy shape is somewhat reminiscent of galaxy merger simulations which don't involve the production of new stars, the disc-like structure is comparable with merger simulations involving star formation.

"This highlights the importance of combining lessons learned from both types of past simulation for better understanding galaxy evolution in the future," said Associate Professor Graham.

"One of the reasons this emerald cut galaxy was hard to find is due to its dwarf-like status: it has 50 times less stars than our own Milky Way galaxy, plus its distance from us is equivalent to that spanned by 700 Milky Way galaxies placed end-to-end.

"Curiously, if the orientation was just right, when our own disc-shaped galaxy collides with the disc-shaped Andromeda galaxy about three billion years from now we may find ourselves the inhabitants of a square looking galaxy."

The results will be published in The Astrophysical Journal.

Rare Rectangle Galaxy Discovered
Universe Today | Jason Major | 2012 Mar 20

Astronomers Discover Rectangular Galaxy
Technology Review | Physics arXiv Blog | kfc | 2012 Mar 20

ScienceShot: Galaxy Is a Rare Gem
Science NOW | Sid Perkins | 2012 Mar 21

LEDA 074886: A remarkable rectangular-looking galaxy - Alister W. Graham et al

• arXiv.org > astro-ph > arXiv:1203.3608 > 16 Mar 2012

[neufer]

[b][color=#FF0000]Piet Hein roundabout in Sergels Torg[/color][/b]

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<<A superellipse, also known as a Lamé curve is a geometric figure defined in the Cartesian coordinate system as the set of all points (x, y) with

where n, a and b are positive numbers. The general Cartesian notation of the form comes from the French mathematician Gabriel Lamé (1795–1870) who generalized the equation for the ellipse.

Though he is often credited with its invention, the Danish poet and scientist Piet Hein (1905–1996) did not discover the super-ellipse. In 1959, city planners in Stockholm, Sweden announced a design challenge for a roundabout in their city square Sergels Torg. Piet Hein's winning proposal was based on a superellipse with n = 2.5 and a/b = 6/5. As he explained it: "Man is the animal that draws lines which he himself then stumbles over. In the whole pattern of civilization there have been two tendencies, one toward straight lines and rectangular patterns and one toward circular lines. There are reasons, mechanical and psychological, for both tendencies. Things made with straight lines fit well together and save space. And we can move easily — physically or mentally — around things made with round lines. But we are in a straitjacket, having to accept one or the other, when often some intermediate form would be better. To draw something freehand — such as the patchwork traffic circle they tried in Stockholm — will not do. It isn't fixed, isn't definite like a circle or square. You don't know what it is. It isn't esthetically satisfying. The super-ellipse solved the problem. It is neither round nor rectangular, but in between. Yet it is fixed, it is definite — it has a unity."

Sergels Torg was completed in 1967. Meanwhile Piet Hein went on to use the superellipse in other artifacts, such as beds, dishes, tables, etc. By rotating a superellipse around the longest axis, he created the superegg, a solid egg-like shape that could stand upright on a flat surface, and was marketed as a novelty toy.

In 1968, when negotiators in Paris for the Vietnam War could not agree on the shape of the negotiating table, Balinski, Kieron Underwood and Holt suggested a superelliptical table in a letter to the New York Times. The superellipse was used for the shape of the 1968 Azteca Olympic Stadium, in Mexico City.

Waldo R. Tobler developed a map projection, the Tobler hyperelliptical projection, published in 1973, in which the meridians are arcs of superellipses.

Hermann Zapf's typeface Melior, published in 1952, uses superellipses for letters such as o. Many web sites say Zapf actually drew the shapes of Melior by hand without knowing the mathematical concept of the superellipse, and only later did Piet Hein point out to Zapf that his curves were extremely similar to the mathematical construct, but these web sites do not cite any primary source of this account. Thirty years later Donald Knuth built into his Computer Modern type family the ability to choose between true ellipses and superellipses.

Three connected superellipses are used in the logo of the Pittsburgh Steelers.>>

[bystander]

Square galaxy is a rebel
New Scientist | Astrophile | Celeste Biever and Stephen Battersby | 2012 Mar 21

Object type: Dwarf galaxy
Location: Eridanus constellation

If a person is square they are a bit dull, but for a galaxy, it is the mark of a true rebel. A rectangular galaxy spotted 70 million light years from Earth is the boxiest galaxy known – and could bring a new understanding of how galaxies form and evolve.

Galaxies take on one of three shapes: a flattened circular disc typically hosting a spiral pattern of stars like our Milky Way, an ellipsoid – like a rugby ball or American football – or an irregular shape without clear symmetry. Box-like galaxies are virtually unheard of, says Alister Graham at the Swinburne University of Technology in Hawthorn, Victoria, Australia.

Graham is one of the researchers who discovered the rectangular galaxy - named LEDA 074886 - while using the Subaru and Keck telescopes in Hawaii to look for globular clusters of stars swarming around NGC 1407, a bright giant galaxy in the constellation Eridanus.

"It's one of those things that just makes you smile because it shouldn't exist, or rather, you don't expect it to exist," says Graham.

Side-on cylinder

LEDA 074886 is a dwarf galaxy, a type much smaller than our Milky Way. His team aren't sure what its three-dimensional shape is. One possibility is that it is an inflated disc that more closely resembles a cylinder and that looks like a rectangle because we view it side-on from Earth.

"The alternative shape, a cube, seems too bizarre to contemplate," says Alister, although he points out that stars with "box orbits" are already documented.

If it is a cylinder, how might it be formed? One option is gravitational torques from its giant neighbour, NGC1407. The trouble is that this wouldn't explain another curious thing about LEDA 074886: at its heart is an edge-on inner disc of young stars, 8000 light years across (see the black disc, in picture above).

Another option is that the angular galaxy formed out of the collision of two spiral galaxies. The impact threw the pre-existing stars from these galaxies into large orbits, creating the rectangular outline, while the gas sank to the middle and condensed to form the central disc of new stars.

Hybrid merger

That would suggest that LEDA's formation was a hybrid of two known types of galaxy formation. The outer rectangular shape is consistent with simulations of elliptical galaxy mergers, which don't involve the production of new stars because these galaxies don't contain much gas. The disc, on the other hand, is more similar to simulations of mergers of gassy galaxies, which involve star formation. "The hybrid nature of LEDA 074886 suggests that both types of event have occurred," says Graham.

"We can now combine lessons learned from both types of simulations," he adds. That might be useful for modelling other galaxies containing both old and young stars.

The researchers suspect that the inner disc may be "precessing" as well as spinning – rather like the way a spinning top both spins on its own axis and turns around the main vertical axis of rotation, says Graham.

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[geckzilla]

Is there a better picture of it somewhere? Because when I look at the picture in the article, a rectangle is not what I see. I see this:

[bystander]

From the paper, there's this:



And the Swinburne article had this:


Click to enlarge

[geckzilla]

Yeah, I realized I was only looking at the third post in the thread after I'd already made my post. Oops. I don't get the double disc impression from the inverted picture as much as I do that false color one. Not sure why, since they are essentially the same thing.