SDSS DR7 superclusters. Morphology (original) (raw)
Related papers
SDSS superclusters: morphology and galaxy content
Astronomy & Astrophysics, 2014
Context. Understanding the formation, evolution and present-day properties of the cosmic web and objects forming it is an important task in cosmology. Aims. We compare the galaxy populations in superclusters of different morphology in the nearby Universe (180 h −1 Mpc ≤ d ≤ 270 h −1 Mpc) to see whether the inner structure and overall morphology of superclusters are important in shaping galaxy properties in superclusters. Methods. We find supercluster morphology with Minkowski functionals and analyse the probability density distributions of colours, morphological types, stellar masses, star formation rate (SFR) of galaxies, and the peculiar velocities of the main galaxies in groups in superclusters of filament and spider types, and in the field. We test the statistical significance of the results with the KS test.
Astronomy & Astrophysics, 2011
Aims. We study the morphology of a set of superclusters drawn from the SDSS DR7. Methods. We calculate the luminosity density field to determine superclusters from a flux-limited sample of galaxies from SDSS DR7, and select superclusters with 300 and more galaxies for our study. We characterise the morphology of superclusters using the fourth Minkowski functional V 3 , the morphological signature (the curve in the shapefinder's K 1 -K 2 plane) and the shape parameter (the ratio of the shapefinders K 1 /K 2 ). We investigate the supercluster sample using multidimensional normal mixture modelling. We use Abell clusters to identify our superclusters with known superclusters and to study the large-scale distribution of superclusters.
Supercluster properties as a cosmological probe
Monthly Notices of the Royal Astronomical Society, 2002
We investigate the supercluster shape properties of the all-sky observed (Abell/ACO) and simulated (Virgo data) cluster catalogues using an approach based on differential geometry. We identify rich superclusters by applying the percolation algorithm to both observed and mock cluster populations, the latter being constructed following the observational selection of the Abell/ACO sample, extended out to z max # 0:114. We apply a set of shape diagnostics in order to study the morphological features of superclusters with $8 cluster members. Our results demonstrate that filamentarity is the dominant supercluster shape feature. On comparing data and models, we show that the LCDM ðV L ¼ 1 2 V m ¼ 0:7Þ model performs better than tCDM, which is excluded at a relatively high confidence level, in agreement with other recent large-scale structure studies.
The morphological types of galaxies in the Local Supercluster
Proceedings of the International Astronomical Union, 2014
On the basis of the Hyper – Leda Catalogue HyperLeda 8293 galaxies with heliocentric radial velocities below 2500 km s-1 were selected; 4570 had known morphological types (4366 had calculated b/a ratio). We checked the frequency of the distribution of various types in the LSC, finding spirals and irregulars most numerous, in accordance with expectations. The axial ratio of galaxy diameters of various types was studied, and the dependence of this parameter on the morphological type was noted.
The richest superclusters. I. Morphology
arXiv (Cornell University), 2007
Context. Superclusters are the largest systems in the Universe to give us information about the formation and evolution of structures in the very early Universe. Our present series of papers is devoted to the study of the morphology and internal structure of superclusters of galaxies. Aims. We study the morphology of the richest superclusters from the catalogs of superclusters of galaxies in the 2dF Galaxy Redshift Survey and compare the morphology of real superclusters with model superclusters in the Millennium Simulation. Methods. We use Minkowski functionals and shapefinders to quantify the morphology of superclusters: their sizes, shapes, and clumpiness. We generate empirical models of simple geometry to understand which morphologies correspond to the supercluster shapefinders (Appendix A). Results. Rich superclusters have elongated, filamentary shapes with high-density clumps in their core regions. The clumpiness of superclusters is determined using the fourth Minkowski functional V 3. In the K 1-K 2 shapefinder plane the morphology of superclusters is described by a curve which is characteristic of multi-branching filaments as shown by our empirical models. We found several differences between observed and model superclusters. The curves of the fourth Minkowski functional V 3 for observed and model superclusters have different shapes indicating that their structure is different. The values of V 3 for the supercluster SCL126 (the Sloan Great Wall) show that this supercluster has a very high density core which is absent in other superclusters. The values of the shapefinders H 1-H 3 and K 1 and K 2 for observed superclusters have much larger scatter than for model superclusters. The differences between the fourth Minkowski functional V 3 for the bright and faint galaxies in observed superclusters are larger than in simulated superclusters. Conclusions. Our results show how the Minkowski functionals and shapefinders can be used to describe the morphology of superclusters: their shapes, sizes and clumpiness. The shapes of observed superclusters are more diverse than the shapes of simulated superclusters. The larger scatter of the fourth Minkowski functional V 3 for the bright and faint galaxies for observed superclusters compared to simulated superclusters is an indication that the clumpiness of bright and faint galaxies in models does not reflect well the clumpiness of different galaxies in observed superclusters. Our results suggest also that the volume covered by the Millennium Simulations may be too small to properly describe the large morphological variety of superclusters.
Characteristic density contrasts in the evolution of superclusters. The case of A2142 supercluster
Astronomy & Astrophysics, 2015
Context. The formation and evolution of the cosmic web in which galaxy superclusters are the largest relatively isolated objects is governed by a gravitational attraction of dark matter and antigravity of dark energy (cosmological constant). Aims. We study the characteristic density contrasts in the spherical collapse model for several epochs in the supercluster evolution and their dynamical state. Methods. We analysed the density contrasts for the turnaround, future collapse, and zero gravity in different ΛCDM models and applied them to study the dynamical state of the supercluster A2142 with an almost spherical main body, making it a suitable test object to apply a model that assumes sphericity. Results. We present characteristic density contrasts in the spherical collapse model for different cosmological parameters. The analysis of the supercluster A2142 shows that its high-density core has already started to collapse. The zero-gravity line outlines the outer region of the main body of the supercluster. In the course of future evolution, the supercluster may split into several collapsing systems. Conclusions. The various density contrasts presented in our study and applied to the supercluster A2142 offer a promising way to characterise the dynamical state and expected future evolution of galaxy superclusters.
The dynamical evolution of stellar superclusters
Monthly Notices of the Royal Astronomical Society, 1998
Recent images taken with the Hubble Space Telescope (HST) of the interacting disk galaxies NGC 4038/4039 (the Antennae) reveal clusters of many dozens and possibly hundreds of young compact massive star clusters within projected regions spanning about 100 to 500 pc. It is shown here that a large fraction of the individual star clusters merge within a few tens to a hundred Myr. Bound stellar systems with radii of a few hundred pc, masses < ∼ 10 9 M ⊙ and relaxation times of 10 11 − 10 12 yr may form from these. These spheroidal dwarf galaxies contain old stars from the pre-merger galaxy and much younger stars formed in the massive star clusters, and possibly from later gas-accretion events. The possibility that star formation in the outer regions of gas-rich tidal tails may also lead to super clusters is raised. The mass-to-light ratio of these objects is small, because they contain an insignificant amount of dark matter. After many hundred Myr such systems may resemble dwarf spheroidal satellite galaxies with large apparent mass-to-light ratia, if tidal shaping is important.
Structure and dynamics of the supercluster of galaxies SC0028-0005
Monthly Notices of the Royal Astronomical Society, 2015
According to the standard cosmological scenario, superclusters are objects that have just passed the turnaround point and are collapsing. The dynamics of very few superclusters have been analysed up to now. In this paper, we study the supercluster SC0028-0005, at redshift 0.22, identify the most prominent groups and/or clusters that make up the supercluster, and investigate the dynamic state of this structure. For the membership identification, we have used photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 10, finding six main structures in a flat spatial distribution. We have also used a deep multiband observation with MegaCam/Canada-France-Hawaii Telescope to estimate de mass distribution through the weak-lensing effect. For the dynamical analysis, we have determined the relative distances along the line of sight within the supercluster using the Fundamental Plane of early-type galaxies. Finally, we have computed the peculiar velocities of each of the main structures. The 3D distribution suggests that SC0028-005 is indeed a collapsing supercluster, supporting the formation scenario of these structures. Using the spherical collapse model, we estimate that the mass within r = 10 Mpc should lie between 4 and 16 × 10 15 M. The farthest detected members of the supercluster suggest that within ∼60 Mpc the density contrast is δ ∼ 3 with respect to the critical density at z = 0.22, implying a total mass of ∼4.6-16 × 10 17 M , most of which in the form of low-mass galaxy groups or smaller substructures.
2013
Abstract. We present a study of the shape, size, and spatial orientation of superclusters of galaxies. Approximating superclusters by triaxial ellipsoids we show that superclusters are flattened, triaxial objects. We find that there are no spherical superclusters. The sizes of superclusters grow with their richness: the median semi-major axis of rich and poor superclusters (having ≥8 and < 8 member clusters) is 42 and 31 h −1 Mpc, respectively. Similarly, the median semi-minor axis is 12 and 5 h −1 Mpc for rich and poor superclusters. The spatial orientation of superclusters, as determined from the axes of ellipsoids, is nearly random. We do not detect any preferable orientation of superclusters, neither with respect to the line of sight, nor relative to some other outstanding feature in the large scale structure, nor with respect to the directions of principal axes of adjacent superclusters.
The properties of galaxies in supercluster filaments
2007
Superclusters appear as large-scale structures in the form of a network of filaments, and can be up to 100 h −1 100 Mpc in extent. In this dissertation, we investigate in detail the spatial structure of the three richest superclusters of galaxies closer to us then z=0.1. We investigate the rate of star formation in galaxies at various positions among the filaments and clusters in the Pisces-Cetus Supercluster. We use an index of star formation derived from a principal component analysis of optical spectra. We have shown that galaxies which are members of these filaments, show a steady decline in star formation rate, from the periphery of a cluster, into the cluster core. However, on top of this trend, we find a nearly instantaneous enhancement of the rate of star formation at ∼ 3 h −1 70 Mpc from its centre. We conclude that the most likely reason for this sudden enhancement in star formation rate is galaxy-galaxy harassment. Further work shows that the enhancement in star formation occurs mainly in the infalling dwarf galaxies (−20 < M B < −17.5) and that there is little evidence Publications Publications in Refereed Journals 1. The Pisces-Cetus Supercluster a remarkable filament of galaxies in the 2dF