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Paper: Dust Emission from Stephan’s Quintet
Volume: 421, Galaxies in Isolation: Exploring Nature Versus Nurture
Page: 272
Authors: Natale, G.; Tuffs, R.; Popescu, C.; Xu, C. K.; Fischera, J.; Lu, N.; Appleton, P.; Dopita, M.; Sulentic, J.; Gao, Y.; Yun, M.; Reach, W.; Boulanger, F.; Ogle, P.; Duc, P. A.; des Forets, G. P.
Abstract: We present new infrared images of the prototype of compact galaxy groups, Stephan’s Quintet, taken with Spitzer/MIPS at 24, 70 and 160μm, and compare these with existing images at X-ray (Trinchieri et al. 2005, ,here- after T05), UV/optical (Xu et al. 2005) and radio wavelengths (Williams et al. 2002) as well as with archival Spitzer/IRAC imaging at 8μ m. Morphological decomposition of the new images reveal an extended (on scales of up to 70 kpc) component of FIR emission which is roughly correlated with diffuse soft X-ray emission arising from the SHOCK and HALO regions (see T05). This correlation could be due, in principle, to collisional heating of dust embedded in X-ray plasma. If active, this mechanism would determine a significant shortening of the gas cooling time scale because the luminosity of the X-ray correlated infrared emission is about 70 times higher than the X-ray luminosity. However the color of dust emission and the inferred dust to gas ratio, comparable to the solar neighbourhood value, are difficult to explain in terms of purely collisionally heated dust. It is plausible that dust in colder and denser gas phases, heated by the diffuse intergalactic radiation field and/or local radiation fields from embedded young stars, is the major source of the apparently extended emission. The presence of the extended infrared emission, not related to the main bodies of the galaxies, is probably a direct consequence of the interaction induced decoupling between gas and stars in Stephan’s Quintet. Gas displacement has also modified the location of star formation sites (as traced by compact sources in the Spitzer images and the UV) compared to the case of isolated galaxies. In Stephan’s Quintet most of the recent star formation appears to have occurred at the peripheries of the galaxies, extending into the intergalactic medium.
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