scholarly journals The Galaxy Content of Clusters

1977 ◽  
Vol 4 (1) ◽  
pp. 253-260 ◽  
Author(s):  
Augustus Oemler
Keyword(s):  
Small Groups ◽  
Matter Content ◽  
Point Of View ◽  
Clusters Of Galaxies ◽  
Cluster Galaxies ◽  
Physical Environments ◽  
The Galaxy ◽  
Points Of View ◽  
Galaxy Populations ◽  
The Universe

Clusters of galaxies are easily identifiable collections of galaxies, all at the same distance and all observed under similar conditions of galactic obscuration, etc. They are, therefore, very convenient samples with which to study the matter content of the universe. However, clusters are also very particular physical environments, and from this latter point of view it is their atypical character which is of interest. The differences in the contents of one cluster from another, and of each from the contents of small groups and the “field” can teach us much about how the properties of galaxies depend on the environments in which they were born and have evolved.Because of the interrelatedness of these two points of view, one cannot really understand the galaxy populations of clusters until one also understands the populations of galaxies which are not in clusters. Therefore, while this review will concentrate on the contents of rich clusters of galaxies, it will also be necessary to discuss the properties of non-cluster galaxies.

scholarly journals The Westerbork Survey of Rich Clusters of Galaxies

1980 ◽  
Vol 5 ◽  
pp. 715-721 ◽  
Author(s):  
Edwin A. Valentijn
Keyword(s):  
Luminosity Function ◽  
Point Of View ◽  
Clusters Of Galaxies ◽  
Radio Luminosity ◽  
General Reference ◽  
Statistical Point ◽  
Cluster Galaxies ◽  
Luminosity Functions ◽  
The Galaxy ◽  
Radio Luminosity Function

In the Westerbork Survey of Rich Clusters of galaxies (WSRC), seven nearby and rich clusters of galaxies have been observed with the Westerbork Synthesis Radio Telescope. The results obtained at different frequencies are published in several papers of a series, and Table 1 serves as a general reference to these publications. In these papers, both discussions on individual radio sources and the presentation of cluster radio luminosity functions (RLF) are given. Here we summarize some of the results of the WSRC which, from a statistical point of view, impose some constraints on the rate of the radio activity of galaxies and on the influence of the galaxy environments on their activity. The rate of radio activity of a sample of galaxies in a cluster can be described by the integral RLF of the cluster, which represents the fraction of galaxies that emit in the radio domain above a certain power. When it is presented as a function of the optical luminosities of the cluster galaxies, it is called the bivariate radio luminosity function (BRLF). The BRLFs are most suitable for representing in an unbiased way the rate of activity of a sample of galaxies, since they are presented in absolute parameters and are normalized to the optical luminosity function (or distribution) of the galaxy samples. This is important since, both inside and outside clusters, it has been shown that the RLF depends strongly on the optical luminosities.

scholarly journals Reconstructing Orbits of Galaxies in Extreme Regions (ROGER) II: reliability of projected phase-space in our understanding of galaxy populations

2021 ◽  
Author(s):  
Valeria Coenda ◽  
Martín de los Rios ◽  
Hernán Muriel ◽  
Sofía A Cora ◽  
Héctor J Martínez ◽  
...  
Keyword(s):  
Phase Space ◽  
Galaxy Formation ◽  
Formation Rate ◽  
Stellar Mass ◽  
Cluster Galaxies ◽  
The Galaxy ◽  
Galaxy Populations ◽  
Galaxy Population ◽  
2D Data ◽  
Good Agreement

Abstract We connect galaxy properties with their orbital classification by analysing a sample of galaxies with stellar mass M⋆ ≥ 108.5h−1M⊙ residing in and around massive and isolated galaxy clusters with mass M200 > 1015h−1M⊙ at redshift z = 0. The galaxy population is generated by applying the semi-analytic model of galaxy formation sag on the cosmological simulation MultiDark Planck 2. We classify galaxies considering their real orbits (3D) and their projected phase-space position using the roger  code (2D). We define five categories: cluster galaxies, galaxies that have recently fallen into a cluster, backsplash galaxies, infalling galaxies, and interloper galaxies. For each class, we analyse the 0.1(g − r) colour, the specific star formation rate (sSFR), and the stellar age, as a function of the stellar mass. For the 3D classes, we find that cluster galaxies have the lowest sSFR, and are the reddest and the oldest, as expected from environmental effects. Backsplash galaxies have properties intermediate between the cluster and recent infaller galaxies. For each 2D class, we find an important contamination by other classes. We find it necessary to separate the galaxy populations in red and blue to perform a more realistic analysis of the 2D data. For the red population, the 2D results are in good agreement with the 3D predictions. Nevertheless, when the blue population is considered, the 2D analysis only provides reliable results for recent infallers, infalling galaxies and interloper galaxies.

scholarly journals Dragging Force on Galaxies Due to Streaming Dark Matter

1990 ◽  
Vol 124 ◽  
pp. 645-649
Author(s):  
Tetsuya Hara ◽  
Shigeru Miyoshi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Rest Frame ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
The Universe

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.

scholarly journals Testing Cosmological Models with Clusters of Galaxies

1999 ◽  
Vol 183 ◽  
pp. 221-228
Author(s):  
S. Gottlöber ◽  
J. Retzlaff ◽  
A. Klypin
Keyword(s):  
Statistical Tests ◽  
Large Fraction ◽  
Mass Scale ◽  
Clusters Of Galaxies ◽  
Matter Distribution ◽  
Redshift Surveys ◽  
The Galaxy ◽  
Redshift Survey ◽  
Formation And Evolution ◽  
The Universe

Currently little is known about the mass distribution on intermediate scales between those probed by deep redshift surveys of galaxies and those probed by COBE. Catalogs of galaxy clusters reach depths of several hundred megaparsecs, and, thus, are very useful for those scales. Only the Las Campanas Redshift Survey (LCRS) is comparable with that depth. However, the LCRS samples only narrow slices whereas cluster catalogs cover a large fraction of the sky. Clusters seems to be the most suitable objects to fill the gap between scales probed by COBE and the galaxy samples. Moreover, clusters are advantageous over galaxies as probes of the matter distribution in the Universe because our understanding of its formation and evolution is better established than it is for galaxies. Clusters are high peaks (mass scaleM≃ 1015M⊙) in the density field, which have collapsed relatively recently. Because of that, it is easy to identify clusters in numerical simulations. But the number of clusters is much smaller than the number of galaxies, which makes the statistics of clusters noisier. Nevertheless, clusters are exceptionally useful objects for the investigation of the matter distribution on scales well above 100h–1Mpc. Thus, it is worth to apply different statistical tests to these objects.

scholarly journals OSCILLATING UNIVERSE AS EIGENSOLUTIONS OF COSMOLOGICAL SCHRÖDINGER EQUATION

2000 ◽  
Vol 09 (02) ◽  
pp. 143-154 ◽  
Author(s):  
S. CAPOZZIELLO ◽  
A. FEOLI ◽  
G. LAMBIASE
Keyword(s):  
Schrödinger Equation ◽  
Schrodinger Equation ◽  
Large Scale ◽  
Periodic Structures ◽  
Point Of View ◽  
Correlation Lengths ◽  
Cosmological Expansion ◽  
The Galaxy ◽  
The Universe ◽  
Natural Way

We propose a cosmological model which could explain, in a very natural way, the apparently periodic structures of the universe, as revealed in a series of recent observations. Our point of view is to reduce the cosmological Friedman–Einstein dynamical system to a sort of Schrödinger equation whose bound eigensolutions are oscillating functions. Taking into account the cosmological expansion, the large scale periodic structure could be easily recovered considering the amplitudes and the correlation lengths of the galaxy clusters.

Quasi-periodical structures in the galaxy populations: mass and luminosity functions for the cluster galaxies

1993 ◽  
Vol 202 (1) ◽  
pp. 33-43 ◽  
Author(s):  
V. F. Litvin ◽  
F. M. Holzmann ◽  
A. V. Smirnov ◽  
B. S. Taibin ◽  
V. V. Orlov ◽  
...  
Keyword(s):  
Cluster Galaxies ◽  
Luminosity Functions ◽  
The Galaxy ◽  
Galaxy Populations

scholarly journals Interacting dark energy in f(T) cosmology: A dynamical system analysis

2015 ◽  
Vol 24 (07) ◽  
pp. 1550046 ◽  
Author(s):  
Sujay Kr. Biswas ◽  
Subenoy Chakraborty
Keyword(s):  
Dark Energy ◽  
System Analysis ◽  
Evolution Equations ◽  
Matter Content ◽  
Point Of View ◽  
Interacting Dark Energy ◽  
Quantum Stability ◽  
Transformation Of Variables ◽  
The Universe ◽  
Friedmann Robertson Walker

This paper deals with an interacting dark energy (DE) model in the framework of f(T) cosmology. A cosmologically viable form of f(T) is chosen (T is the torsion scalar in teleparallelism) in the background of flat homogeneous and isotropic Friedmann–Robertson–Walker (FRW) spacetime model of the universe. The matter content of the universe is chosen as dust interacting with minimally coupled scalar field. The evolution equations are reduced to an autonomous system of ordinary differential equations by suitable transformation of variables. The nature of critical points is analyzed by evaluating the eigenvalues of the linearized Jacobi matrix and stable attractors are examined from the point of view of cosmology. Finally, both classical and quantum stability of the model have been discussed.

scholarly journals Scaling Properties of Galaxy Groups

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 139
Author(s):  
Lorenzo Lovisari ◽  
Stefano Ettori ◽  
Massimo Gaspari ◽  
Paul A. Giles
Keyword(s):  
Scaling Laws ◽  
Thermal Evolution ◽  
Matter Content ◽  
Point Of View ◽  
Scaling Relations ◽  
Scaling Properties ◽  
Galaxy Groups ◽  
Gravitational Processes ◽  
General Physical ◽  
The Universe

Galaxy groups and poor clusters are more common than rich clusters, and host the largest fraction of matter content in the Universe. Hence, their studies are key to understand the gravitational and thermal evolution of the bulk of the cosmic matter. Moreover, because of their shallower gravitational potential, galaxy groups are systems where non-gravitational processes (e.g., cooling, AGN feedback, star formation) are expected to have a higher impact on the distribution of baryons, and on the general physical properties, than in more massive objects, inducing systematic departures from the expected scaling relations. Despite their paramount importance from the astrophysical and cosmological point of view, the challenges in their detection have limited the studies of galaxy groups. Upcoming large surveys will change this picture, reassigning to galaxy groups their central role in studying the structure formation and evolution in the Universe, and in measuring the cosmic baryonic content. Here, we review the recent literature on various scaling relations between X-ray and optical properties of these systems, focusing on the observational measurements, and the progress in our understanding of the deviations from the self-similar expectations on groups’ scales. We discuss some of the sources of these deviations, and how feedback from supernovae and/or AGNs impacts the general properties and the reconstructed scaling laws. Finally, we discuss future prospects in the study of galaxy groups.

scholarly journals Galaxy Population in the Infall Regions of Intermediate Redshift Clusters

2006 ◽  
Vol 2 (S235) ◽  
pp. 254-254
Author(s):  
Miguel Verdugo ◽  
Bodo L. Ziegler
Keyword(s):  
Star Formation ◽  
X Ray ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Galaxy Populations ◽  
Cluster Cores ◽  
Galaxy Population ◽  
Special Environment

AbstractWe investigate the galaxy populations in 6 clusters of different x-ray luminosities at intermediate redshifts (z ≈ 0.25) concentrating on their star formation activity. Our ~500 Calar Alto MOSCA spectra come from targets covering large fields out to 2–4 cluster virial radii. To probe this so-called infall region is important since here newly arriving galaxies from the surrounding field encounter the special environment of clusters for the first time. We selected 3 fields containing 2 clusters each from the X-ray Dark Cluster Survey (Gilbank et al. 2004). Results for one field were already published by Gerken et al. 2004.We find evidence that the process(es) that suppresses or truncates the star formation activity in cluster galaxies, sets in already at rather large distances from the cluster cores corresponding to low projected local galaxy densities. This changes the fraction of star forming galaxies rather quickly.

scholarly journals AGNs in Shakhbazian Compact Groups

2002 ◽  
Vol 184 ◽  
pp. 87-88
Author(s):  
A.S. Amirkhanian ◽  
A.G. Egikian ◽  
H. Tiersch ◽  
D. Stoll
Keyword(s):  
Emission Line ◽  
Environmental Influence ◽  
Compact Groups ◽  
Clusters Of Galaxies ◽  
Broad Line ◽  
Groups Of Galaxies ◽  
Cluster Galaxies ◽  
The Galaxy ◽  
Emission Line Galaxies ◽  
The Difference

The results of CCD spectroscopic observations of Shakhbazian compact groups of galaxies (SHCGs) with the 1.54-m (La Silla, Chile), 2.2-m (Calar Alto, Spain) and 2.6-m (Byurakan) telescopes are presented. According to these preliminary data, about 10% of member galaxies in SHCGs are emission-line galaxies (ELGs) including the broad-line AGNs (of classical Seyfert 1 type) and the narrow-emission-line galaxies.A research program has been developed in the University of Potsdam, Potsdam Astrophysikalisches Institut in cooperation with other observatories (particularly with Byurakan Astrophysical Observatory) to perform photometric and spectroscopic investigations of galaxies in the SHCGs. Within the framework of this program the redshift (radial velocity) measurements have been carried out for more than 200 galaxies in 36 SHCGs. The MIDAS software package was used for processing and interpreting of the galaxy spectra. Most of these redshifts were measured for the first time. 180 member galaxies (90%) in these groups have absorption spectra typical of E and SO galaxies. Twenty galaxies (10%) turn out to be ELGs. They are in the range 0.02 ≤ z ≤ 0.17, i.e., the SHCGs lie in approximately the same redshift space as Abell clusters. These compact groups contain predominantly elliptical and lenticular galaxies (del Olmo 1988; Amirkhanian 1989) like the cores of rich, regular, centrally condensed clusters of galaxies. The fraction of spirals falls in the densest matter concentrations. On the other hand, it is a well-established fact that in the local universe the active objects tend to avoid the cores of dense clusters of galaxies (e.g. Green and Yee 1984). That is why the discovery of an emission-line population with broad-line AGNs in SHCGs (Tiersch et al. 1999) was unexpected. As shown by Dressier, Thompson and Shectman (1985) in their sample of 1268 galaxies in the feilds of 14 rich clusters the ELGs comprise 31% of the field galaxies but only 7% of the cluster galaxies. Similarly, according to their statistics AGNs make up 5% of the field sample, but only 1% of the cluster sample. They note that the difference in the distribution of morphological types can only partially explain this effect. Obviously, some sort of environmental influence is present.

Sign in / Sign up

Export Citation Format

Share Document