scholarly journals Faint Structures in Low Density Regions of the Nearby Universe

1999 ◽  
Vol 183 ◽  
pp. 256-256
Author(s):  
U. Lindner ◽  
K.J. Fricke ◽  
J. Einasto ◽  
M. Einasto
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Morphological Type ◽  
High Density ◽  
Low Density ◽  
Clusters Of Galaxies ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Empty Sphere ◽  
First Time

We present an investigation of the galaxy distribution in the huge underdense region between the Hercules, Coma and Local Superclusters, the so-called Northern Local Void (NLV), using void statistics (for details refer to Lindner et al. this Volume). Reshift data for galaxies and poor clusters of galaxies are available in low and high density regions as well. Samples of galaxies with different morphological type and various luminosity limits have been studied separately and void catalogues have been compiled from three different luminosity limited galaxy samples for the first time. Voids have been found using the empty sphere method which has the potential to detect and describe subtle structures in the galaxy distribution. Our approach is complementary to most other methods usually used in Large–Scale Structure studies.

scholarly journals Regularity of the Large-Scale Structure of the Universe

1999 ◽  
Vol 183 ◽  
pp. 169-177
Author(s):  
J. Einasto
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
High Density ◽  
Low Density ◽  
Clusters Of Galaxies ◽  
The Universe

The observed structure of the Universe is hierarchical. Galaxies and clusters of galaxies are concentrated within elongated filamentary chains of various richness. High-density regions of the Universe form superclusters consisting of one or several clusters of galaxies and chains of galaxies surrounding and joining clusters. The space between filaments is void of galaxies. Superclusters and voids form a continuous network of alternating high- and low-density regions in the Universe.

scholarly journals A kinematic confirmation of the hidden Vela supercluster

2019 ◽  
Vol 490 (1) ◽  
pp. L57-L61 ◽  
Author(s):  
Hélène M Courtois ◽  
Renée C Kraan-Korteweg ◽  
Alexandra Dupuy ◽  
Romain Graziani ◽  
Noam I Libeskind
Keyword(s):  
Excellent Agreement ◽  
Mass Concentration ◽  
Large Scale ◽  
Milky Way ◽  
Large Scale Structure ◽  
Peculiar Velocity ◽  
The Galaxy ◽  
Zone Of Avoidance ◽  
First Time ◽  
The Universe

ABSTRACT The Universe region obscured by the Milky Way is very large and only future blind large H i redshift, and targeted peculiar surveys on the outer borders will determine how much mass is hidden there. Meanwhile, we apply for the first time two independent techniques to the galaxy peculiar velocity catalogue CosmicFlows−3 in order to explore for the kinematic signature of a specific large-scale structure hidden behind this zone: the Vela supercluster at cz ∼18 000 km s−1. Using the gravitational velocity and density contrast fields, we find excellent agreement when comparing our results to the Vela object as traced in redshift space. The article provides the first kinematic evidence of a major mass concentration (knot of the Cosmic Web) located in the direction behind Vela constellation, pin pointing that the Zone of Avoidance should be surveyed in detail in the future.

scholarly journals Mapping the Large-Scale Structure

1994 ◽  
Vol 161 ◽  
pp. 669-686
Author(s):  
V. de Lapparent
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Theoretical Models ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Nearby Galaxy ◽  
Redshift Surveys ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Microwave Background Radiation

The nearby galaxy distribution suggests a remarkable structure in which large voids are delineated by dense walls of galaxies in a cell-like pattern. The nearby voids range in diameter from ∼ 10 to ∼ 50h− 1 Mpc. Deeper surveys appear to be consistent with the nearby distribution and show no evidence of voids larger than ∼ 100h −1 ∗ Mpc. We might thus have reached the scale where the universe becomes homogeneous. The size of the largest inhomogeneities in the galaxy distribution is an important issue because it can put tight constraints on the theoretical models when confronted by the high degree of isotropy of the microwave background radiation. Comparison of the various existing redshift surveys emphasizes the need for systematic redshift surveys over significant areas of the sky out to intermediate and large distances. Although deep pencil-beam surveys are best suited for probing a large number of voids and walls, understanding the nature of the intercepted peaks and valleys in terms of large-scale structure requires that the angular coverage of the surveys be larger than the galaxy auto-correlation length. If this condition is not satisfied, the size of the voids and the density contrast of the walls can be overestimated.

scholarly journals A Unified Picture of Large-Scale Structure

1992 ◽  
Vol 9 ◽  
pp. 671-680
Author(s):  
Neta A. Bahcall
Keyword(s):  
Cellular Structure ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Low Density ◽  
Pencil Beam ◽  
Clusters Of Galaxies ◽  
Different Types ◽  
Consistent Picture ◽  
The Universe

AbstractA consistent picture of large-scale structure appears to be emerging from different types of observations including the spatial distribution of galaxies, clusters of galaxies, narrow pencil-beam surveys, and quasars. I describe these observations below. A network of large-scale superclusters, up to ~ 150 Mpc in scale, is suggested. The supercluster network surrounds low-density regions of similar scales, suggesting a “cellular” structure of the universe. (Ho = 100 km /s/ Mpc is used).

scholarly journals Tracing Large-Scale Structure with Galaxy Objective-Prism Spectra

1988 ◽  
Vol 130 ◽  
pp. 525-525
Author(s):  
Q.A. Parker ◽  
H.T. Macgillivray ◽  
S.M. Beard
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Early Type ◽  
Galaxy Distribution ◽  
Large Numbers ◽  
The Galaxy ◽  
Measured Sample ◽  
Objective Prism ◽  
Low Dispersion

A new and promising use of galaxy objective-prism spectra as a means of highlighting features in the large scale galaxy distribution has been recently reported by Parker et al. (1987). The technique relies on the property that galaxies with identifiable 4000Å features in low dispersion objective-prism spectra are mostly ellipticals (Cooke, 1980), and that early type galaxies seem to delineate structure and clumpiness in the galaxy distribution (e.g. Giovanelli and Haynes, 1982). The effect is most striking when large numbers of objective-prism galaxy spectra are considered. Figure 1 gives the X-Y plot for 1539 galaxies with 4000Å features to Bj=18.7 in one UKST field out of a manually measured sample of 2903 galaxy prism spectra. Substantial clumpiness is evident. This technique can trace structure in the galaxy distribution across many UKST fields to depths of 400 h−1Mpc.

The Galaxy Distribution and the Large-Scale Structure of the Universe

1986 ◽  
Vol 470 (1 Twelfth Texas) ◽  
pp. 123-135
Author(s):  
MARGARET J. GELLER ◽  
VALÉRIE LAPPARENT ◽  
MICHAEL J. KURTZ
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
The Universe

scholarly journals The High-energy X-ray Background and Limits on Large Scale Structure

1988 ◽  
Vol 130 ◽  
pp. 203-206
Author(s):  
A. Mészáros ◽  
P. Mészáros
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Large Scale Structure ◽  
High Energy ◽  
Scale Structure ◽  
High Density ◽  
Low Density ◽  
X Ray ◽  
Clustering Model ◽  
X Ray Background

At present there are in use three different models to characterize the large scale structure of the universe. The clustering model (Soneira and Peebles, 1978) assumes that the superclusters are high density islands in a low density sea. The void model (Joeveer and Einasto, 1978), on the other hand, assumes that the voids are isolated low density islands in a high density sea. The sponge model (Gott et al., 1986) assumes that high and low density regions occupy equal volumes, and that the high and low density regions are both connected. The straightforward way to decide among these three models is the direct investigation of the spatial distribution of the galaxies. Nevertheless, there is an essentially different observational method that may also be useful to obtain some information about these models. The X-ray background radiation (XRB) is due either to the bremsstrahlung of hot intergalactic gas, or to the sum of the radiation of unresolved discrete sources (E.G. Boldt 1987). If the “discrete” origin is correct, then obviously the actual number of sources, and hence their total intensity, may vary from one part of the sky to another. Thus, in this case one has the possibility to estimate the number of sources in a given volume from the observed isotropy of the XRB. For example, Hamilton and Helfand (1987) suggest that the number of sources must be larger than 5000/(degree)2. Any such estimate needs several assumptions. In the previous works one usually assumed that the sources were distributed completely randomly; see, e.g. Fabian (1972). Nevertheless, if the XRB is generated by young galaxies (Bookbinder et al. 1980), it is not excluded that the sources of the SRB are also grouped similarly to galaxies. Because in this case the distribution of sources of the XRB is not completely random, one may expect a different type of fluctuations in the intensity of the XRB. In addition, since the grouping may be quite different for the three structure models, the expected fluctuations may also be different. There is a chance to discriminate among them using the observed isotropy of XRB. The basic observational datum concerning the isotropy of the XRB is well-known: the fluctuations in the intensity are smaller than 3%, if 3° × 3° pixels are used Shafer (1983).

scholarly journals Density Profiles of Clusters of Galaxies

1977 ◽  
Vol 4 (1) ◽  
pp. 246-251
Author(s):  
Neta A. Bahcall
Keyword(s):  
High Density ◽  
Low Density ◽  
Clusters Of Galaxies ◽  
Surface Distribution ◽  
Density Profiles ◽  
Number Of Clusters

Data on the surface distribution of galaxies in a number of clusters has been given by several authors (see, for example, Shane & Wirtanen 1954; Zwicky 1956, 1957; Omer, Page & Wilson 1965; Clark 1968; Noonan 1971, 1974; Bahcall 1971, 1972a, b, 1973a, b, 1974, 1975; Rudnicki 1963; Rudnicki & Baranauska 1966a, b; Rood et al. 1972; Rood & Sastry 1972; Oemler 1974; Austin & Peach 1974a, b; Chincarini & Rood 1975, 1976; and references quoted therein). The distributions show a relatively smooth fall-off from a high density at the center of the cluster to a low density tail at the outskirts of the cluster. Secondary maxima or subclustering are sometimes superimposed on an otherwise smooth and monotonic profile.

scholarly journals Large-Scale Structure in the Universe: Spatial Distribution and Peculiar Velocities

1987 ◽  
Vol 124 ◽  
pp. 335-348
Author(s):  
Neta A. Bahcall
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Large Scale Structures ◽  
Peculiar Velocities ◽  
Scale Structures ◽  
The Universe

The evidence for the existence of very large scale structures, ∼ 100h−1Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. Detection of a ∼ 2000 kms−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016.5M⊙ and may contain a larger amount of dark matter than previously anticipated.

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