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7. ENTRAINMENT OF COOL GAS

Buoyantly rising bubbles transport energy and magnetic fields outward into clusters. In addition, these rising bubbles create channels in the ICM, and entrain cool cluster gas from the center outward, where it will be mixed with hotter gas.

This type of entrainment is seen clearly in M87 in the Virgo cluster (Young et al. 2002). In this system, the X-ray temperature map reveals that an arc of cool gas follows the same path as the radio lobes. The metallicity in the arc is somewhat higher than the surroundings, which is consistent with the picture of the gas in the arc originating closer to the cluster center, where the average metallicity is higher than in the outer regions of the cluster.

An additional example is Abell 133 (Fujita et al. 2002). This cluster includes a radio source that is offset from the center of the cluster. The radio source was originally thought to be a radio relic, likely produced from a merger shock. The Chandra image revealed a filament connecting the radio source with the cluster center. The filament is cool, and shows no evidence of shocks. Fujita et al. surmise that the radio emission is probably a detached lobe from the central AGN. The lobe may have been displaced by the motion of the cD or through buoyancy. The filament of X-ray emission is likely to be cool gas that was entrained outward from the center of the cluster by the radio source.

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