Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Galaxy Merger Leaves Behind Telltale Blue Arc

18.10.2002


Astronomers have identified the vivid scar of a cosmic catastrophe: a blue arc thousands of light years long produced when a galaxy pulled in a smaller satellite galaxy and tore it apart.


Visible in the upper right corner of this image of the Centaurus A Galaxy is an arc of blue stars left behind when Centaurus A pulled in a smaller galaxy and tore it apart. Astronomers say the scar from this cosmic collision is fairly new and thousands of light years long.
Note: Image is available without arrows. Follow this link.
Photo by Eric Peng/JHU/NOAO



The streak is composed of clusters of young blue stars that formed as the larger galaxy, Centaurus A, absorbed the smaller galaxy about 200 million to 400 million years ago. Researchers will report in the December Astronomical Journal that their discovery suggests absorption of smaller galaxies may be a significant contributor to the formation of galactic halos, outer perimeters of galaxies where star populations are sparse.

"This adds a nice example in the local universe to the growing evidence that galaxy halos are built up from the accretion of dwarf satellite galaxies," said Eric Peng, a graduate student in astronomy in the Krieger School of Arts and Sciences at The Johns Hopkins University and lead author of the new paper. "These halos are interesting partly because they’re hard to study, but also because time scales for things to happen in halos are very long, which means they may preserve conditions that reveal how a galaxy formed and evolved."


Peng and his colleagues found the streak in specially processed digital images of Centaurus A taken at the National Science Foundation’s Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory near La Serena, Chile. The team made its observations in 2000.

At 10 million light years from our galaxy, Centaurus A (which is visible with binoculars in the southern hemisphere’s night sky, but not visible at all in the northern hemisphere) is quite close in galactic terms. The galaxy’s most prominent features include a central lane of dust and debris, and signs of violent activity on its perimeter that are suggestive of a prior galactic merger.

Astronomers had previously noticed the arc that Peng and colleagues have now identified as a galactic merger remnant, but without recognizing its origin. That took evidence Peng and colleagues gathered with Mosaic II, a new wide-field digital camera at the Blanco Telescope funded by the National Optical Astronomy Observatory.

Peng and fellow researchers Holland Ford, a professor of astronomy at Johns Hopkins; Ken Freeman, a professor at the Australian National University; and Rick White, astronomer at the Space Telescope Science Institute, used Mosaic II to create images of Centaurus A through several different color filters. Comparing these images highlighted regions of the galaxy that have different colors, and revealed the predominance of young blue stars in the arc. This allowed Peng and his colleagues to identify the arc as a remnant of a galactic merger and estimate the time when Centaurus A absorbed it.

Astronomers have identified similar remnants of galactic mergers in various stages of ingestion into the Milky Way, including the Sagittarius Galaxy. Peng said the newly identified remnant in Centaurus A is unusual in terms of both how recently the merger took place and how gas-rich the satellite galaxy appears to have been.

Ford noted that the group hadn’t originally set out to find remnants of dwarf galaxies.

"One of the joys of science is unexpected discoveries," Ford said. "Although our pictures were taken for another project, we decided to search the data for evidence of ’shredded’ dwarf galaxies. We were very excited when the blue arc popped out of one of the images."

Peng noted that the remnant cannot account for all the signs of prior galactic merger activity seen in Centaurus A. As an elliptical (or roughly football- shaped) galaxy, Centaurus A was likely produced by the merger of two large galaxies.

"It’s possible that the small galaxy that was recently accreted by Centaurus A was originally a satellite orbiting one of the large galaxies involved in that larger merger," says Peng. "Just like when our galaxy merges with the Andromeda Galaxy in the distant future -- the Milky Way’s satellite galaxies, such as the Magellanic Clouds, will likely be involved in that merger."

Peng and other researchers are currently looking for other signs of remnants elsewhere in Centaurus A, and planning for follow-up observations on the arc they identified as a galactic remnant.

"If we can get the velocities of star clusters in the arc and map out the orbit, that will allow us to place better constraints on how long ago the merger occurred and on what the motions of the incoming galaxy were," Peng says.

Michael Purdy | EurekAlert!

More articles from Physics and Astronomy:

nachricht Midwife and signpost for photons
11.12.2017 | Julius-Maximilians-Universität Würzburg

nachricht New research identifies how 3-D printed metals can be both strong and ductile
11.12.2017 | University of Birmingham

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Midwife and signpost for photons

11.12.2017 | Physics and Astronomy

How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas

11.12.2017 | Earth Sciences

PhoxTroT: Optical Interconnect Technologies Revolutionized Data Centers and HPC Systems

11.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>