What Do These Images Tell Us?
In the Chandra X-ray image of N132D made with the High Resolution Camera, the regions of brightest X-ray emission are shown in yellow. The N132D supernova remnant appears to be colliding with a giant molecular cloud, which produces the brightening on the southern rim of the remnant. The relatively weak x-radiation on the upper left shows that the shock wave is expanding into a less dense region on the edge of the molecular cloud. A number of small circular structures are visible in the central regions and a hint of a large circular loop can be seen in the upper part of the remnant. The expanding shock wave has swept up material equal to that of 600 suns.
The optical image shows gas that has a temperature of a few tens of thousands of degrees, much lower than the 10 million degree X-ray emitting gas. The similarity of the two images is striking, but a detailed examination shows important differences. The optical shell is not as complete, and some of the clumps in the interior are known to have high concentrations of the element oxygen. These are believed to have been ejected in the explosion, which must have occurred about 3,000 years ago.
The radio emission from N132D is due to "synchrotron radiation" from high-energy electrons (moving very nearly at the speed of light) spiraling in the magnetic field of the supernova remnant. The radio structure traces out regions where there are concentrations of high-energy electrons and the magnetic field is strong. This is expected to occur near shock waves, which explains the similarity in appearance between the radio and X-ray images. However, note that the radio emission is strong in the X-ray "hole" at the lower right. This could be due to a bubble of high-energy electrons, or a strong magnetic field region which has pushed the hot gas away.
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