Maryland scientists in team studying oddball galaxy

Maryland scientists among those studying galaxy and wondering: what the heck is this?

As part of a research team studying galaxies, two University of Maryland scientists recently helped find a wild one.

It doesn't fit into the two main galaxy shape categories and is even a bit too odd to belong with those astronomers call "irregulars," although loosely speaking it is. It appears in one respect a conventional spiral galaxy, but also in a class by itself, a cosmic eccentric dropping clues about galaxies and the mysterious objects believed to lie at the center of most of them: supermassive black holes.

University of Maryland astronomy professor Sylvain Veilleux and doctoral student Vicki Toy have been trailing this galaxy along with 11 researchers from other institutions, and — in a recent development in the field — help from amateur astronomers through such websites as Galaxy Zoo. Their research report appeared online last month and is scheduled to be in print next month in the Monthly Notices of the Royal Astronomical Society.

Couched in the customary clusters of mathematical equations and graphs, the research report begins telling the story of a galaxy that — like nearly all of the 700,000 galaxies loosely classified so far, a fraction of the total in the universe — is identified only by catalog number: J1649+2635.

It's about 800 million light years from Earth, which in astronomical terms is in the neighborhood, and about the size of our own galaxy, the Milky Way: roughly 80,000 light years across. For some sense of scale, consider that one light year — the distance light travels in a vacuum in 365 days — is nearly 6 trillion miles. That's about 100 million trips from Baltimore to California and back again.

J1649+2635 is a "grand design spiral," meaning it shows well-defined spiral arms emanating in unbroken lengths from the center. In that respect it resembles the Milky Way, also a spiral, and conforms to one of the main established galaxy types.

Other features, however, set it apart, challenging some standing notions about galaxies. The anomalies are yet to be explained.

It has two elongated structures shooting out of it: jets or plumes of subatomic particles — mostly likely electrons and protons — that are emitting non-visible radio energy.

That's odd, as such jets are usually found in elliptical galaxies, which contain stars that are older than those found in spirals. This is only the fourth spiral galaxy found so far to emit these jets. It is also the first "grand design" galaxy to show a "halo" of visible light around it, probably the glow of a vast cloud of stars.

The researchers got onto J1649+2635 by following up information compiled on the Galaxy Zoo website, which allows anyone to look at images of galaxies and sort them into categories.

"Without Galaxy Zoo, this object wouldn't have made it in our preliminary sample and we wouldn't have observed it at all," Veilleux said. "I was a bit skeptical of the concept at first, but the Galaxy Zoo has shown time and time again that it is a valuable resource for professional astronomers."

The halo emerged as a clear structure in Toy's visual observations using the Discovery Channel Telescope in the Coconino National Forest, about 40 miles southeast of Flagstaff, Ariz. The halo that was considered a possibility from galaxy surveys came into sharp focus as Toy took repeated images in early June, the last of four trips she made to the telescope last year.

"I'm taking short images," Toy said, and she would "stack them until you see a nice complete object."

Confirmation of the halo and the spiral structure through visual observation were two key contributions by Veilleux and Toy to the effort that involved 12 universities and observatories, including the department of astronomy and the Joint Space-Science Institute at the University of Maryland, College Park.

They could be clues about the formation of galaxies and the behavior of supermassive black holes, with masses several hundred million times the sun. These behemoths are Veilleux's chief research interest.

Black holes are not exactly "holes" in the sense of empty space, but objects of great mass, with a gravitational force so powerful that they trap light and anything else in their proximity. As a result, they can't be detected through light, radio waves or other conventional means of astronomical observation, presenting a blank spot, a "hole" in the fabric of space. Astronomers usually find them by detecting the hot material in the vicinity of the hole.

Scientists are still figuring out the role these objects play in the life of galaxies, but they believe that supermassive black holes lie at the center of the largest ones, including the Milky Way. (Located on an outer arm of the galaxy, the Earth is in no danger of being sucked in.)

The jets are understood to be generated by the supermassive black hole at the center of the galaxy, so they "may say something about the spin of the black hole," said Philip F. Hopkins, an assistant professor of theoretical astrophysics at the California Institute of Technology.

Hopkins, who was not involved in the research, said the work is "particularly important for trying to understand how those jets came to exist" and how they affect other parts of the galaxy.

He wondered if the galaxy provides a snapshot of a relatively elusive transitional phase in the life of a galaxy, one that lasts only, say, a billion years or so.

Veilleux said the unusual halo around this galaxy could be explained by the merger of two galaxies.

"It's very unlikely that something like that could be created without a merger," Veilleux said. The spiral structure, he said, would have been formed after the merger.

Scientists believe elliptical galaxies — shaped like an ellipse with no spiral arms — and the largest galaxies of all kinds have been created by mergers.

This research points back to the heavens, Veilleux said, as scientists seek more galaxies with this mix of features, trying to understand just how odd J1649+2635 really is, and what it means.

arthur.hirsch@baltsun.com

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