The X-ray Emission Of Member Galaxies In Clusters

Galaxy clusters are gravitationally bound systems consisting of member galaxies,diffuse hot gas,and dark matter.As the celestial bodies connecting galaxies and cosmic large-scale structures,galaxy clusters play an important role in the formation and evolution of galaxies.The cluster consists of dozens or even thousands of member galaxies,mostly old elliptical galaxies,surrounded by intracluster medium(ICM).The brightest cluster galaxy of the member galaxies,usually near the center of the cluster's gravitational trap,has a mass much greater than that of other member galaxies.Due to the special position of the member galaxies in the cluster,the member galaxies and the cluster are interrelated and interacted with each other.Studies have shown that member galaxies and clusters are co-evolving.Therefore,the study of the member galaxies in the cluster helps to reveal the influence of environment on the evolution of galaxies.At the same time,the center of the galaxy usually contains supermassive black holes,and the X-ray emission of member galaxies is thought to be associated with the activity of the galactic nuclei.The X-ray emission of member galaxies is of great significance for the study of supermassive black holes in the center of the galaxy and the environment of the galaxy clusters.Due to the difficulty of sample making and the number of member galaxies with X-ray emission is very small,there are few related studies on X-ray radiation of member galaxies.As a result,many problems have not been solved clearly,such as the statistical nature of X-ray emission in member galaxies;the relationship between the origin of X-ray emission of member galaxies and the galaxies themselves and the environment;the source of accretion material of supermassive black holes.The key to solving these problems is to get a large sample of reliable X-ray member galaxies.WHL12 is the largest sample of optical galaxy clusters,which was confirmed by the team members and contains 132,684 galaxy clusters.Containing 1972,101 optical member galaxies,it is the largest sample of member galaxies.And the information about the member galaxies has not yet been released,which provides primary data for our study.The3XMM-DR5 is currently the largest X-ray source table.The current largest X-ray member galaxies sample can be obtained by cross-certification.The sample we obtained contained 252X-ray member galaxies,37 of which were the brightest cluster galaxies.This paper will mainly introduce the identification process of the sample,and use this X-ray member galaxies sample to study the X-ray emission of the cluster galaxies.In the first work,we studied the statistical properties of X-ray member galaxies using the advantage of large sample data,and found that the optical clusters contained very few X-ray member galaxies.The distribution of surface number density of X-ray member galaxies with the normalized radius was studied,and it was found that the surface number density of X-ray member galaxies increased with the decrease of cluster radius.Galaxy clusters with the x-ray brightest cluster galaxy were found to be the densest in the center of cluster.The X-ray luminosity of member galaxies did not change significantly with the normalized radius.We also studied the environmental dependence of the X-ray emission of member galaxies.The optical richness of clusters is a proxy for their mass,and we found that the more X-ray member galaxies detected in the cluster with high richness,suggesting that the X-ray emission of member galaxies may be dependent on the cluster environment.However,using the current data samples,there is no obvious relationship between the X-ray luminosity of member galaxies and the optical richness of clusters or the optical absolute magnitude of galaxies.The second work is to study the relationship between the X-ray emission and the optical spectrum lines of member galaxies using the optical spectrum lines information provided by the Sloan digital sky survey(SDSS).By crossing the sample of X-ray member galaxies with the MPA-JHU data table,we found that most of the optical classification of the 30 X-ray member galaxies is AGN,and all of the X-ray brightest cluster galaxies are LINERS.We also found a strong correlation between the X-ray luminosity of the member galaxies and the luminosity of the H??H??[Nii]6584?[Oiii]5007 these four optical emission spectra.From the optical band,it is shown that the X-ray emission of the member galaxies is probably related to the activity of the central active galactic nucleus.Finally,we summarize the main work and conclusions of this paper,and propose some ideas for future research work.