Origin of the M-94 (NGC 4736) Outer Disk Spiral Arms

The presence of bars at the center of galaxies can introduce instabilities that result in the formation of spiral arms. Interestingly, galactic bars can be quite broad. These fat bars, also known as oval distortions, often resemble a normal, slightly inclined disk with spiral arms. Previous researchers considered the inner disk of M94(NGC 4736) to be an oval distortion. The results of our team's study supports their conclusions and considers it to be the most plausible explanation for the inner ring, the previously undetected spiral structure and enhanced new star formation in the outer disk of M94 (NGC 4736).

This animation simulates the development of spiral arms in the outer disk surrounding M94 (NGC 4736) from the dynamic effect of the galaxy's central oval distortion on the rest of the galaxy. This N-body model was computed by Dr. Inma Martinez-Valpuesta (Instituto de Astrof´isica de Canarias)

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    Animation Image copyright ©2009 Inma Martinez-Valpuesta (Instituto de Astrof´isica de Canarias, Departamento de Astrof´isica, Universidad de La Laguna)