Galaxy infall by interacting with its environment: a comprehensive study of 340 galaxy clusters
2016
To study systematically the evolution of the angular extents of the
galaxy,
intracluster medium(ICM), and dark matter components in
galaxy clusters, we compiled the optical and X-ray properties of a sample of 340 clusters with
redshifts<0.5, based on all the available data from the Sloan
Digital Sky Surveyand Chandra/XMM-Newton. For each cluster, the member
galaxieswere determined primarily with
photometric redshiftmeasurements. The radial ICM
mass distribution, as well as the total gravitational
mass distribution, was derived from a spatially resolved spectral analysis of the X-ray data. When normalizing the radial profile of
galaxynumber to that of the ICM mass, the relative curve was found to depend significantly on the cluster
redshift; it drops more steeply toward the outside in lower-
redshiftsubsamples. The same evolution is found in the
galaxy-to-total mass profile, while the ICM-to-total mass profile varies in an opposite way. The behavior of the
galaxy-to-ICM distribution does not depend on the cluster mass, suggesting that the detected
redshiftdependence is not due to mass-related effects, such as sample selection bias. Also, it cannot be ascribed to various
redshift-dependent systematic errors. We interpret that the
galaxies, the ICM, and the dark matter components had similar angular distributions when a cluster was formed, while the
galaxiestraveling in the interior of the cluster have continuously fallen toward the center relative to the other components, and the ICM has slightly expanded relative to the dark matter although it suffers strong radiative loss. This cosmological
galaxy
infall, accompanied by an ICM expansion, can be explained by considering that the
galaxiesinteract strongly with the ICM while they are moving through it. The interaction is considered to create a large energy flow of 1044?45 erg s?1 per cluster from the member
galaxiesto their environment, which is expected to continue over cosmological timescales.
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