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 Comet or asteroid? Hubble discovers that a unique object is a binary
21.09.2017 | NASA/Goddard Space Flight Center

nachricht First users at European XFEL
21.09.2017 | European XFEL GmbH

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: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Comet or asteroid? Hubble discovers that a unique object is a binary

21.09.2017 | Physics and Astronomy

Cnidarians remotely control bacteria

21.09.2017 | Life Sciences

Monitoring the heart's mitochondria to predict cardiac arrest?

21.09.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>