The morphology of clusters of galaxies: the cluster-galaxy

connection

Irini Sakelliou

Birmingham : T. PonmanMPIA : S. Falter, V. Smolcic, E. BellMPE : A. FinoguenovColorado: P. Motl

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How structure is formed

The formation of a Coma-like cluster.

Left panels : Dark matterRight panels : Hot gas

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Galaxy-Cluster interactionsThey should affect both : the cluster and its

galaxies

An infalling galaxy in A2125 (z~0.25) Chandra/HST/VLA/KPNO images 01-06-04 NASA press release

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Temperature mapsContours= surface brightness

How/when and at which stage of cluster formation a) the galaxies are affected/tranformed and b) the ICM is affected by the infalling material?

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Simple measures of the structure. That it can work with X-ray and optical and

simulated images

• Centroid offset : Determination of the centre of the distribution in annuli of increasing radius. The annuli are not concentric.

• Ellipticity

• Position Angle

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Ellipticity & Position angle

Accumulation of counts (cnt) along circular annuli (). If the 2D distribution is elliptical the cnt- plot should have 2 peaks. The shape of the cnt- plot depends on the ellipticity and the position angle.

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Abell 2255XMM-Newton image in the (0.3 - 10.0) keV energy range(~14ks MOS exposure) Abell 2255 is a ~7keV at z=0.08

SDSS cluster galaxies.Red circle = XMM FOV

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High-z cluster at z=0.22 from COSMOS (Smolcic et al. 2006)

It is a poor cluster, in the process of merging with other groups. X-ray contoursRed cluster galaxiesBlue galaxies

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A2255: Centroid offset

X-rays: ICM distribution Optical : galaxy distribution

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Ellipticity & Position angle

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A2255: position angle

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Summary, Concluding remarks, & future

• A simple method to determine the dynamical ‘age’ of clusters from X-ray and optical observations

• There are still problems to be solved (e.g., errors)

• We need simple methods for determining the structure of clusters if we want to go higher redshifts

• Use simulated X-ray images to set the baseline

z= 0.25

Simulated X-ray images from Motl et al.2004

z= 0.00