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Galaxy and mass assembly : search for a population of high-entropy galaxy groups.

Pearson, R. J. and Ponman, T. J. and Norberg, P. and Robotham, A. S. G. and Babul, A. and Bower, R. G. and McCarthy, I. G. and Brough, S. and Driver, S. P. and Pimbblet, K. (2017) 'Galaxy and mass assembly : search for a population of high-entropy galaxy groups.', Monthly notices of the Royal Astronomical Society., 469 (3). pp. 3489-3504.


Observations with the ChandraX-ray Observatory are used to examine the hot gas properties within a sample of 10 galaxy groups selected from the Galaxy And Mass Assembly survey's optical Friends-of-Friends group catalogue. Our groups have been screened to eliminate spurious and unrelaxed systems, and the effectiveness of this procedure is demonstrated by the detection of intergalactic hot gas in 80 per cent of our sample. However, we find that 9 of the 10 are X-ray underluminous by a mean factor of ∼4 compared to typical X-ray-selected samples. Consistent with this, the majority of our groups have gas fractions that are lower and gas entropies somewhat higher than those seen in typical X-ray-selected samples. Two groups, which have high 2σ lower limits on their gas entropy, are candidates for the population of high-entropy groups predicted by some active galactic nucleus feedback models.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017. The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:03 May 2017
Date deposited:18 July 2017
Date of first online publication:06 May 2017
Date first made open access:18 July 2017

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