A New Method to Quantify X-ray Substructures in Clusters of Galaxies
  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
S\'ersic 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 0.02<z<0.2 and have a signal-to-noise ratio 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 signal-to-noise observations. We find
no evidence of correlation between the substructure level and physical
properties of the clusters such as mass, gas temperature, X-ray luminosity and
redshift. The scaling relations for the two sub-samples (high and low
substructure level clusters) are different (they present an off-set, 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.
