MessageToEagle.com - NGC 5907 is sometimes called the "Splinter" or Knife Edge Galaxy because of its unusual appearance.
It is a spiral galaxy lying in the Dragon constellation, about 40 million light-years from Earth that
could have been formed through a gigantic collision of galaxies, 8 to 9 billion years ago.
It reveals a system of stellar currents forming gigantic loops in its surrounding halo.
Researchers of the Observatoire de Paris, CNRS, Chinese Academy of Sciences, National Astronomical Observatories of China and
Aix-Marseille Université, say that the galaxy shows extraordinary large loops and currents of stars in its surrounding halo.
They have performed simulations with 200 000 to 6 million particles and calculations, that including gas hydrodynamics,
are able to reproduce in a film the formation of NGC5907 and its surrounding gigantic loops of matter.
During the last 9 billions years, most probably half of spiral galaxies have been formed due to numerous cosmic
collisions.
The spiral galaxy NGC5907 seems to be one of them.
The galaxy's gigantic loops may represent the relic of a gigantic collision between galaxies of similar sizes,
which would have occurred 8 to 9 billion years ago.
Previously the 150 000 light-years loops surrounding NGC5907 were believed to be associated to the capture of
a very small satellite that would have lost its matter relatively recently.
New simulations are excluding satellite masses that would be below one twelfth of the main galaxy.
It also implies that the progenitors of NGC5907 and its loops were very gas rich, at least with gas fraction of 60%.
Interestingly the new scenario can be easily falsified, as it predicts the presence of other, even larger but
fainter, loops that could be observed in the near future.
Already the new Chinese year appears to be fruitful for the French-Chinese collaboration, and possibly this
year will see an interesting confirmation of what is the best scenario for making large spiral galaxies.
On left, the NGC 5907 galaxy. It is compared to the simulations, on right. Both cases show an edge-on galactic disk surrounded by giant
loops of old stars, which are witnessing of a former, gigantic collision.Credits: Jay Gabany, cosmotography.com/
Observatoire de Paris / CNRS / Pythéas / NAOC)
Numerical simulations have been made using 32- and 196-core computers at the Paris Observatory center and
the 680-core Graphic Processor Unit supercomputer of Beijing NAOC with the capability to run 50000 billion
operations per second.
The smoothed particle hydrodynamical treeSPH code GADGET2 is a free software to
which has been implemented a full description of star formation and all cooling and other physical processes.
Results appeared on the cover of the online edition of Astronomy and Astrophysics, the 13 February 2012.
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MessageToEagle.com - NGC 5907 is sometimes called the "Splinter" or Knife Edge Galaxy because of its unusual appearance.
These objects are very rare. A discoverer of one of them even named it a "pathological galaxy".
The formation of stellar-mass black holes through the collapse of massive stars is well accepted. However,
it is not yet completely clear how the supermassive objects are formed.
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