8-12 juin, 2014


Substructure and Gas Clumping in the Outskirts of Abell 133

Gandhali Joshi (McMaster University)

Dr. Michael Balogh, University of Waterloo Dr. Brian McNamara, University of Waterloo

Recent observations have found entropy profiles in galaxy cluster outskirts that are shallower than predicted and values of f_gas that are higher than the Universal baryon fraction inferred from the Cosmic Microwave Background (CMB). Abell 133 is an ideal candidate for studying this phenomenon, since it has been observed in a wide (R≈30') Chandra mosaic with an exposure time of ∼2 Ms. The X-ray imaging is combined with existing optical imaging and spectroscopy to search for any possible gas clumps and to study their properties. Spectroscopy obtained on the cluster yields ~180 cluster members which give a cluster redshift of z=0.05610.0002 and a velocity dispersion of σ=74343 km/s. About 30 overdensities with radius ≥ 30" are detected as gas clumps on the X-ray image. The galaxy distribution in these clumps is analyzed, both for the stacked signal as well as the individual clumps, to find any significant red sequences associated with them. Several of these clumps appear to be background systems, some consisting of 1-2 galaxies, others being small groups or clusters. Only 2-3 clumps appear to be associated with the cluster itself. This suggests that the cluster density profile is actually quite smooth, which may not agree with numerical simulations. Further studies are required to determine if the cluster density distribution is consistent with what is predicted and the nature of the background systems.

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