A NEW METHOD TO QUANTIFY X-RAY SUBSTRUCTURES IN CLUSTERS OF GALAXIES

Author(s)

Andrade-Santos, Felipe ^[1] ; Lima Neto, Gastao B. ^[1] ; Lagana, Tatiana F. ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Astron, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 746, n. 2 FEB 20 2012.
• Web of Science Citations: 16

Abstract

We present a new method to quantify substructures in clusters of galaxies, based on the analysis of the intensity of structures. This analysis is done in a residual image that is the result of the subtraction of a surface brightness model, obtained by fitting a two-dimensional analytical model (beta-model or Sersic profile) with elliptical symmetry, from the X-ray image. Our method is applied to 34 clusters observed by the Chandra Space Telescope that are in the redshift range z is an element of {[}0.02, 0.2] and have a signal-to-noise ratio (S/N) greater than 100. We present the calibration of the method and the relations between the substructure level with physical quantities, such as the mass, X-ray luminosity, temperature, and cluster redshift. We use our method to separate the clusters in two sub-samples of high-and low-substructure levels. We conclude, using Monte Carlo simulations, that the method recuperates very well the true amount of substructure for small angular core radii clusters (with respect to the whole image size) and good S/N observations. We find no evidence of correlation between the substructure level and physical properties of the clusters such as gas temperature, X-ray luminosity, and redshift; however, analysis suggest a trend between the substructure level and cluster mass. The scaling relations for the two sub-samples (high-and low-substructure level clusters) are different (they present an offset, i. e., given a fixed mass or temperature, low-substructure clusters tend to be more X-ray luminous), which is an important result for cosmological tests using the mass-luminosity relation to obtain the cluster mass function, since they rely on the assumption that clusters do not present different scaling relations according to their dynamical state. (AU)

• FAPESP's process: 08/05970-0 - Galaxy cluster collisions and their astrophysical consequences
• Grantee: Felipe Andrade Santos
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 08/04318-7 - Intracluster gas enrichment and star formation efficiency in clusters of galaxies
• Grantee: Tatiana Ferraz Laganá
• Support Opportunities: Scholarships in Brazil - Post-Doctoral