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>

Unusual A2142 supercluster with a collapsing core: distribution of light and mass

Einasto, Maret,Gramann, Mirt,Saar, Enn,Liivamä,gi, Lauri Juhan,Tempel, Elmo,Nevalainen, Jukka,Heinä,mä,ki, Pekka,Park, Changbom,Einasto, Jaan EDP Sciences 2015 Astronomy and astrophysics Vol.580 No.-

<P>Context. Superclusters of galaxies can be used to test cosmological models of the formation and evolution of the largest structures in the cosmic web, and of galaxy and cluster evolution in superclusters. Aims. We study the distribution, masses, and dynamical properties of galaxy groups in the A2142 supercluster. Methods. We analyse the global luminosity density distribution in the supercluster and divide the supercluster into the high-density core and the low-density outskirts regions. We find galaxy groups and filaments in these regions, calculate their masses and mass-to-light ratios and analyse their dynamical state with 1D and 3D statistics. We use the spherical collapse model to study the dynamical state of the supercluster. Results. In the A2142 supercluster rich groups and clusters lie along an almost straight line forming the 50h<SUP>−1</SUP> Mpc long main body of the supercluster. The A2142 supercluster has a very high density core surrounded by lower-density outskirts. The total estimated mass of the supercluster is M<SUB>est</SUB> = 6.2 × 10<SUP>15</SUP> M<SUB>⊙</SUB>. More than a half of groups with at least ten member galaxies in the supercluster lie in the high-density core of the supercluster, centred at the X-ray cluster A2142. Most of the groups in the core region are multimodal. In the outskirts of the supercluster, the number of groups is larger than in the core, and groups are poorer. The orientation of the axis of the cluster A2142 follows the orientations of its X-ray substructures and radio halo, and is aligned along the supercluster axis. The high-density core of the supercluster with the global density D8≥17 and perhaps with D8 ≥13 may have started to collapse. Conclusions. A2142 supercluster with collapsing core and straight body, is an unusual object among superclusters. In the course of the future evolution, the supercluster may split into several systems.</P>

국립공원내의 환경오염행위 관리를 위한 Communication정책의 효 과 -미국 Carlsbad Caverns 국립공원의 사례를 중심으로-

김용근,James H. Gramann 한국조경학회 1991 韓國造景學會誌 Vol.19 No.2

Damage to natural resources from inappropriate visitor behavior is a problem faced by National Park management. Based on the data gathered by personal interview and mail questionnaire, this study examines the effects of communication strategies to reduce depreciative behavior in Carlsbad Caverns National Park. One-quarter of Carlsbad Caverns visitors indicates that they have noticed damage to cave formation during their tour. Almost 38% of visitors say that they have witnessed someone touch a formation inside the Caverns. This is a relatively high percentage compared with other depreciative behavior research to refrain from "tattling" on fellow visitors. Two-thirds of the respondents recalls touching formation replicas before entering the Cavern, while almost all visitors (97.9%) say that they have heard the ranger's talk about not touching formation or leaving the trail. Visitors feel that the ranger's talk is more effective in reducing depreciative behavior than the formation replicas, although at least three-fourths of all respondents believes both techniques are effective.

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>