Thermal and Shock Histories of Gas in Galaxy Clusters
Abstract
Galaxy clusters are the most recently formed cosmological objects in the universe, making them ideal for studying the interplay between cosmology and baryonic physics in structure formation. Understanding their formation and growth requires not only an understanding of the baryonic physics, but also the detailed dynamics of how gas accretes from cosmic filaments onto a cluster throughout its lifetime. One of the outstanding questions concerning galaxy clusters currently is the baryon deficit in their interior as well as non-equilibrium phenomena (such as turbulence and gas clumping) in the virialization regions. Recent X-ray and microwave observations have revealed detailed thermodynamic structure of the cluster hot gas from the core to their virial radii, making comparisons of gas accretion in simulations to observations a strong cosmological probe. In this work, we focus on quantifying gas accretion in non-radiative cosmological simulations of galaxy clusters, where the only significant changes in entropy will be due to shock heating. In order to track each gas element, we implemented a tracer particle module in the Adaptive Refinement Tree cosmological simulation code. By following the thermal histories of each tracer particle, we measure the Mach number of every shock the particle experienced and identify periods of significant shock-heating. Combining this with measurements of how the temperature distribution of regions of the halo change over time, we then investigate whether gas had significantly different histories based on whether they accrete straight from the cosmic background or by first accreting onto a subhalo, the change in accretion due to the mass of the final main halo, and the disruptive effect mergers have on the smooth accretion process. We discuss implications of our results for understanding recent deep Chandra X-ray observations of Abell 133 which revealed several unexpected structural features connected to its gas accretion, including a sharp cutoff in diffuse gas and the presence of significant gas clumping at large scales.
- Publication:
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American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22335822B