Computer Science
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........27d&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF MARYLAND COLLEGE PARK, 1994.Source: Dissertation Abstracts International, Volume: 56-04, Section:
Computer Science
5
Scientific paper
This thesis uses a well-defined flux limited sample of galaxy clusters to search for X-ray substructure. To search the inner regions of clusters where the X-ray emission from the cluster is dominant, each cluster is fit with an elliptical model and the model is subtracted from the image. Statistically significant deviations from the fitted model are searched for and if the deviation is more than three sigma above the model then it is considered candidate substructure. The resulting catalog of sources is then matched with catalogs of known optical radio and X-ray sources to eliminate objects such as stars, active galactic nuclei, and quasars. To complete the catalog of substructure to a projected radius of 3 Mpc from the cluster center, sources outside the bright cluster emission are combined with the catalog of sources from the inner regions after eliminating detections of stars, active galactic nuclei, and quasars from the list. The result of this work is that at least 62% of the clusters in this sample have substructure. This percentage of clusters with substructure is much higher than found in previous X-ray studies that have estimated that 30-40% of clusters have substructure. However this high fraction of clusters with substructure does agree with the latest optical studies that show that up to 70% of clusters have substructure. The presence of substructure in clusters is strong evidence that groups and poor clusters are presently falling into clusters. The infall rate of these structures can be estimated if the substructure is infalling radially. A simple model of how the X-ray gas in the cluster interacts with the gas in the substructure, along with the number of clusters where the X-ray gas is associated with optical substructure and the number of clusters with isolated X -ray features yields an infall rate of ~ 1 times 10^ {-10} objects/yr. By extrapolating the correlation between X-ray luminosity and cluster mass determined for richer systems to the low luminosity systems found here, the mass of the infalling objects can be estimated. A mass infall rate of ~10 ^5 M_odot/yr is obtained. This catalog of substructure is the first such catalog using a well defined flux-limited catalog of clusters. The X-ray data allow one to search outside the cluster core where optical searches for substructure have focused. These data reveal that many clusters in this sample have substructure and that the X-ray and optical data show that comparable percentages of clusters have substructure. The X-ray data and the optical data show that substructure is common in clusters and indicate that cluster formation is ongoing at the present epoch.
No associations
LandOfFree
X-Ray Substructure in a Flux-Limited Catalog of Clusters of Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with X-Ray Substructure in a Flux-Limited Catalog of Clusters of Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-Ray Substructure in a Flux-Limited Catalog of Clusters of Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1685302