Probing of the Interactions Between the Hot Plasmas and Galaxies in Clusters from z=0.1 to 0.9
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Asia/Tokyo
RIBF Room 203 (RIKEN)
RIBF Room 203
RIKEN
Description
Lecturer: Dr. GU Liyi (The University of Tokyo)
Language： English
The X-ray emitting hot plasma in galaxies, or the so called intracluster medium (ICM), constitutes about 80-90% of the detected baryon content in clusters. The remaining 10-20% resides in member galaxies, which move through the ICM with transonic speeds. Nearby clusters are generally characterized by galaxies distributions which are much more concentrated than their ICM. Also the ICM is considerably metal enriched up to Mpc scale, much more extended than the stellar component. These and other results led Makishima et al. (2001) to propose "galaxies used to be distributed out to the outer regions of a cluster, but they have gradually fallen, by interacting with surrounding hot plasmas, to the cluster center over the Hubble time".
To probe galaxy infall, we have carried out comprehensive X-ray and optical data analysis on a sample of 34 X-ray bright clusters of galaxies. By measuring radial profiles of galaxy light and ICM mass, we calculated the galaxy light vs ICM mass ratio profile for each cluster. This ratio profiles were found to gradually steepen from z=0.9 to z=0.1, indicating that the stellar component indeed become more concentrated in the ICM sphere towards low redshifts. Such galaxy infall is likely to be caused by the drag exerted from the ICM to the galaxies as they move through the ICM and interact with it, while gravitational drag can enhance the infall of most massive galaxies.