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Predicting Merger-Induced Gas Motions in LCDM Galaxy Clusters | | Daisuke Nagai
; Erwin T. Lau
; Camille Avestruz
; Kaylea Nelson
; Douglas H. Rudd
; | | Date: |
8 Jul 2013 | | Abstract: | In the hierarchical structure formation model, clusters of galaxies form
through a sequence of mergers and continuous mass accretion, which generate
significant random gas motions especially in their outskirts where material is
actively accreting. Non-thermal pressure provided by the internal gas motions
affects the thermodynamic structure of the X-ray emitting intracluster plasma
and introduces biases in the physical interpretation of X-ray and
Sunyaev-Zeldovich effect observations. However, we know very little about the
nature of gas motions in galaxy clusters. The ASTRO-H X-ray mission, scheduled
to launch in 2015, will have a calorimeter capable of measuring gas motions in
galaxy clusters at the level of <100 km/s. In this work, we make a prediction
of the level of gas motions expected in the LCDM model using hydrodynamical
simulations of galaxy cluster formation, focusing on the merger-induced gas
motions. We show that the gas velocity dispersion is larger in more massive
clusters, but exhibits large scatter due to the diversity in their dynamical
states. We show that systems with large gas motions are morphological
disturbed, while early forming, relaxed groups show a smaller level of
merger-induced gas motions. By analyzing mock deep ASTRO-H observations of
simulated clusters, we show that such observations can accurately measure the
gas velocity dispersion in the outskirts of nearby relaxed galaxy clusters.
ASTRO-H analysis of merging clusters, on the other hand, requires
multi-component spectral fitting, which provides rich information about their
dynamical states, such as the peculiar velocities and the velocity dispersion
of gas within individual sub-clusters. Our analyses indicate that the ASTRO-H
mission should be capable of measuring the missing energy associated with
internal gas flows as well as enabling unique studies of substructures in
galaxy clusters. | | Source: | arXiv, 1307.2251 | | Services: | Forum | Review | PDF | Favorites | |
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