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The Large and Small Magellanic Cloud's evolutionary history  @psychohistorian.org

The Large and Small Magellanic Cloud's evolutionary history

posted: 3529 days ago, on Sunday, 2009 Mar 22 at 08:33
tags: astronomy, LMC/SMC.

Two astronomers from the Indian Institute of Astrophysics (Bangalore, India) have studied the structure of the Large and Small Magellanic Clouds using the distribution of so-called red clump stars to provide clues to the galaxy duo's past history.

Red clump stars are intermediate-age stars (older than 1 Gyr) that lie within the intermediate-age disk of a galaxy. The astronomers identified these stars based on photometric data gathered by the OGLE II (Optical Gravitational Lensing Experiment) and MCPS (Magellanic Cloud Photometric Survey) surveys.

Examining the distribution of these disk stars gives a glimpse into the evolution of the host galaxy. For example, if a thick disk is observed, it is likely that some mechanism has disturbed its development.

The LMC and SMC are nearby irregular galaxies at a distance of about 50kpc and 60kpc respectively. Recent proper motion studies indicate that the Clouds may be approaching our Galaxy for the first time and that they might not always have been a binary system.

Thus it isn't clear whether the present-day structure observed in the clouds is modified due to their mutual interactions, interactions with our Galaxy, or something else, like minor merger events.

From their analysis, the astronomers conclude that the two Clouds formed differently, and have different evolutionary pathways.

  1. The LMC is more or less an irregular galaxy with a disk and no bulge, while the SMC appears to be a spheroid.
  2. They also propose that the SMC has a bulge; what was previously thought to be its bar is possibly a deformed bulge.
  3. The LMC seems to have undergone minor mergers, whereas the SMC seems to have experienced tidal forces in addition to minor mergers.
  4. Finally, the LMC has an inner halo, while the SMC does not.

The astronomers conclude that even though the Clouds are located close to each other now, the early formation and evolution of these two galaxies appear different.

Find the full paper ("Depth estimation of the Large and Small Magellanic Clouds", by S. Subramanian and A. Subramaniam) in the latest edition of Astronomy & Astrophysics online at http://www.aanda.org/10.1051/0004-6361/200811029.

nothing more to see. please move along.


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