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About this Image
Stephan's Quintet (SQ) has intrigued astronomers since its discovery
at the Observatoire de Marseille in the 19th century. Originally a quintet, it became a quartet when the brightest galaxy was declared a foreground object unrelated to the other four members that share
similar redshifts. More recently the quintet was re-established when
a fainter galaxy east of the other four was discovered at the same
The active dynamical history in SQ is evident in multifold
observational manifestations of the interaction processes which include the creation of a common halo of stripped stars. Now this
halo is also manifest in the hot intergalactic medium, as clearly
seen in the X-ray images obtained with XMM-Newton.
Previous X-ray observations of SQ have quite distinctly shown the effects of galaxy interactions in a compact and dense environment.
A large scale shock of 40 kpc in size is the most evident feature,
and it shows up as a sharp narrow north-south feature between the
galaxies. Comparison with data at other wavelengths illustrates the complexity of the shock region with shock-related effects prominent
at least in the radio continuum, X-ray and optical line emission.
The XMM-Newton observations provide the strongest evidence for diffuse
emission in SQ: the 2D extent of the diffuse emission in both X-ray and optical light can be inferred from the comparison shown in the figure, where a striking correspondence in shape and extent between diffuse emissions from hot gas and the stellar envelope is evident.
The complex lobe-like structure of this halo presumably reflects a group of galaxies which has not yet reached a state of dynamical relaxation.
Investigator(s): G. Trinchieri, W. Pietsch, J. Sulentic. D. Breitschwerdt
Higher resolution versions of this image may be available, please contact the XMM-Newton HelpDesk.
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