Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mystery spiral arms explained?

11.04.2007
Using a trio of space observatories, astronomers may have cracked a 45-year old mystery surrounding two ghostly spiral arms in the galaxy M106 (NGC 4258).

The results, obtained by a team from the University of Maryland (USA), took advantage of the unique capabilities of the European Space Agency’s XMM-Newton X-ray observatory, NASA’s Chandra X-ray Observatory, and NASA’s Spitzer Space Telescope.


This is a composite image of spiral galaxy M106 (NGC 4258). Optical data from the Digitized Sky Survey is shown in yellow, radio data from the Very Large Array appears purple, X-ray data from Chandra is coded blue, and infrared data from the Spitzer Space Telescope appears red. The anomalous arms appear as purple and blue emission. Credits: NASA/CXC/Univ. of Maryland/A.S. Wilson et al. Optical: Pal.Obs. DSS; IR: NASA/JPL-Caltech; VLA & NRAO/AUI/NSF

M106 (also known as NGC 4258) is a spiral galaxy 23.5 million light-years away, in the constellation Canes Venatici. In visible-light images, two prominent arms emanate from the bright nucleus and spiral outward. These arms are dominated by young, bright stars, which light up the gas within the arms. "But in radio and X-ray images, two additional spiral arms dominate the picture, appearing as ghostly apparitions between the main arms," says team member Andrew Wilson of the University of Maryland. These so-called "anomalous arms" consist mostly of gas.

"The nature of these anomalous arms is a long-standing puzzle in astronomy," says Yuxuan Yang, lead author of the team. "They have been a mystery since they were first discovered in the early 1960s."

By analyzing data from XMM-Newton, Spitzer, and Chandra, the team in Maryland have confirmed earlier suspicions that the ghostly arms represent regions of gas that are being violently heated by shock waves.

It has been previously suggested that the anomalous arms are jets of particles being ejected by a supermassive black hole in M106’s nucleus. But radio observations at the Very Large Array in New Mexico later identified another pair of jets originating in the core. "It is highly unlikely that an active galactic nucleus could have more than one pair of jets," says Yang.

In 2001, another team of astronomers at the University of North Carolina (USA), noted that the two jets are tipped 30 degrees with respect to the disk. But if one could vertically project the jets onto the disk, they would line up almost perfectly with the anomalous arms. Figuring that this alignment was not strictly a matter of chance, the team proposed that the jets heat the gas in their line of travel, forming an expanding cocoon. Because the jets lie close to M106’s disk, the cocoon heats gas in the disk and generates shock waves, heating the gas to millions of degrees and causing it to radiate brightly in X-rays and other wavelengths.

To test this idea, Yang and his colleagues looked at archival spectral observations from XMM-Newton. With XMM-Newton’s superb sensitivity, the team could measure the gas temperature in the anomalous arms and also see how X-rays from the gas are absorbed en route by intervening material.

"One of the predictions of this scenario is that the anomalous arms will gradually be pushed out of the galactic disk plane by jet-heated gas," says Yang. The XMM-Newton spectra show that X-rays are absorbed more strongly in the direction of the northwest arm than in the southeast arm. The results strongly suggest that the southeast arm is partly on the near side of M106’s disk, and the northwest arm is partly on the far side.

The scientists noted that these observations show clear consistency with their scenario. Confirmation of this interpretation has recently come from archival observations from NASA’s Spitzer Space Telescope, whose infrared view shows clear signs that X-ray emission from the northwest arm is being absorbed by warm gas and dust in the galaxy’s disk. Moreover, Chandra’s superior imaging resolution gives clear indications of gas shocked by interactions with the two jets.

Besides addressing the mystery of the anomalous arms, these observations allowed the team to estimate the energy in the jets and gauge their relationship to M106’s central black hole.

Norbert Schartel | alfa
Further information:
http://www.esa.int/esaSC/SEMLVET4LZE_index_0.html

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>