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- 저자 : Deshev, Boris (검색결과 3 건)
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Infalling groups and galaxy transformations in the cluster A2142
Einasto, Maret,Deshev, Boris,Lietzen, Heidi,Kipper, Rain,Tempel, Elmo,Park, Changbom,Gramann, Mirt,Heinä,mä,ki, Pekka,Saar, Enn,Einasto, Jaan Springer-Verlag 2018 Astronomy and astrophysics Vol.610 No.-
<P><I>Context.</I> Superclusters of galaxies provide dynamical environments for the study of the formation and evolution of structures in the cosmic web from galaxies, to the richest galaxy clusters, and superclusters themselves.</P><P><I>Aims.</I> We study galaxy populations and search for possible merging substructures in the rich galaxy cluster A2142 in the collapsing core of the supercluster SCl A2142, which may give rise to radio and X-ray structures in the cluster, and affect galaxy properties of this cluster.</P><P><I>Methods.</I> We used normal mixture modelling to select substructure of the cluster A2142. We compared alignments of the cluster, its brightest galaxies (hereafter BCGs), subclusters, and supercluster axes. The projected phase space (PPS) diagram and clustercentric distributions are used to analyse the dynamics of the cluster and study the distribution of various galaxy populations in the cluster and subclusters.</P><P><I>Results.</I> We find several infalling galaxy groups and subclusters. The cluster, supercluster, BCGs, and one infalling subcluster are all aligned. Their orientation is correlated with the alignment of the radio and X-ray haloes of the cluster. Galaxy populations in the main cluster and in the outskirts subclusters are different. Galaxies in the centre of the main cluster at the clustercentric distances 0.5 h<SUP>−1</SUP> Mpc (<I>D</I>c∕<I>R</I>vir < 0.5, <I>R</I>vir = 0.9 h<SUP>−1</SUP> Mpc) have older stellar populations (with the median age of 10−11 Gyr) than galaxies at larger clustercentric distances. Star-forming and recently quenched galaxies are located mostly at the clustercentric distances <I>D</I>c ≈ 1.8 h<SUP>−1</SUP> Mpc, where subclusters fall into the cluster and the properties of galaxies change rapidly. In this region the median age of stellar populations of galaxies is about 2 Gyr. Galaxies in A2142 on average have higher stellar masses, lower star formation rates, and redder colours than galaxies in rich groups. The total mass in infalling groups and subclusters is <I>M</I> ≈ 6 × 10<SUP>14</SUP> h<SUP>−1</SUP><I>M</I>⊙, that is approximately half of the mass of the cluster. This mass is sufficient for the mass growth of the cluster from redshift <I>z</I> = 0.5 (half-mass epoch) to the present.</P><P><I>Conclusions.</I> Our analysis suggests that the cluster A2142 has formed as a result of past and present mergers and infallen groups, predominantly along the supercluster axis. Mergers cause complex radio and X-ray structure of the cluster and affect the properties of galaxies in the cluster, especially at the boundaries of the cluster in the infall region. Explaining the differences between galaxy populations, mass, and richness of A2142, and other groups and clusters may lead to better insight about the formation and evolution of rich galaxy clusters.</P>
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Supercluster A2142 and collapse in action: infalling and merging groups and galaxy transformations
Einasto, Maret,Gramann, Mirt,Park, Changbom,Kim, Juhan,Deshev, Boris,Tempel, Elmo,Heinä,mä,ki, Pekka,Lietzen, Heidi,Lä,hteenmä,ki, Anne,Einasto, Jaan,Saar, Enn EDP Sciences 2018 Astronomy and astrophysics Vol.620 No.-
<P><I>Context</I>. Superclusters with collapsing cores represent dynamically evolving environments for galaxies, galaxy groups, and clusters.</P><P><I>Aims</I>. We study the dynamical state and properties of galaxies and groups in the supercluster SCl A2142 that has a collapsing core, to understand its possible formation and evolution.</P><P><I>Methods</I>. We find the substructure of galaxy groups using normal mixture modelling. We have used the projected phase space (PPS) diagram, spherical collapse model, clustercentric distances, and magnitude gap between the brightest galaxies in groups to study the dynamical state of groups and to analyse group and galaxy properties. We compared the alignments of groups and their brightest galaxies with the supercluster axis.</P><P><I>Results</I>. The supercluster core has a radius of about 8 <I>h</I><SUP>−1</SUP> Mpc and total mass <I>M</I>tot ≈ 2.3 × 10<SUP>15</SUP> h<SUP>−1</SUP><I>M</I>⊙ and is collapsing. Galaxies in groups on the supercluster axis have older stellar populations than off-axis groups, with median stellar ages 4 − 6 and < 4 Gyr, correspondingly. The cluster A2142 and the group Gr8 both host galaxies with the oldest stellar populations among groups in SCl A2142 having the median stellar age <I>t</I> > 8 Gyr. Recently quenched galaxies and active galactic nuclei (AGNs) are mostly located at virial radii or in merging regions of groups, and at clustercentric distances <I>D</I>c ≈ 6 <I>h</I><SUP>−1</SUP> Mpc. The most elongated groups lie along the supercluster axis and are aligned with it. Magnitude gaps between the brightest galaxies of groups are less than one magnitude, suggesting that groups in SCl A2142 are dynamically young.</P><P><I>Conclusions</I>. The collapsing core of the supercluster, infall of galaxies and groups, and possible merging groups, which affect galaxy properties and may trigger the activity of AGNs, show how the whole supercluster is evolving.</P>
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