Constraints on Intracluster Gas Bulk Motions in Clusters of Galaxies with ASCA

Abstract

The recent detection of Doppler shifts of X-ray spectral lines in the intracluster gas of the Centaurus and Perseus clusters of galaxies with ASCA has raised the question of the frequency of such velocity gradients and their relation to other cluster properties. To address this and improve the sample of ICM velocity gradient candidates we carried out a systematic search of the ASCA archive for clusters with suitable observing conditions that allow full azimuthal mapping of gas velocities near the central regions. Here we present the results of the azimuthal velocity distribution of a sample consisting of the best" observed clusters for velocity analysis. Our sample encompasses clusters with different physical and morphological characteristics, including both well behaved "cooling flow" and dynamically active clusters. The gas temperatures of the clusters in our sample range from 1.4 keV to 6.3 keV. We find velocity substructures in ~ 15% of the clusters in our sample on the order of a few x 1E3 km/s. The significance of the velocity gradients' is greater than 99% in Abell 576 and RXJ0419.6+0225, the clusters where velocity gradients are most significant. The velocity gradients are consistent with transitory and/or rotational bulk motion. The velocity gradients in these clusters are unlikely to be due to projected temperature anisotropies, ASCA PSF, intrachip gain variations, and flux contamination from other sources. Chandra images of these clusters do not show obvious cluster alignments within the field of view covered by ASCA. We also noticed a high frequency (~50%) of anisotropic temperature gradients in the core of "cooling flow" clusters, suggesting the presence of frequent dynamical activity in the core of galaxy clusters.

25 pages, no figures, accepted for publication in Astrophysical Journal Supplement Series. For full version with all figures click on http://www.astro.lsa.umich.edu/~rdupke/icbm_sub.pdf

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• Chandra Observation of the Cooling Flow Cluster Abell 2052
• Mapping small-scale temperature and abundance structures in the core of the Perseus cluster
• Complex Structure of Galaxy Cluster Abell 1689: Evidence for a Merger from X-ray data?
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