Statistics of the Galaxy Distribution

Martı́nez, Vicent J.; Saar, E.

doi:10.1201/9781420036169

Cited by 207 publications

(237 citation statements)

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“…To study galaxy correlations in filaments, we use the two-point correlation function ξ(r) that measures the excess probability of finding two points separated by a vector r compared to that probability in a homogeneous Poisson sample (Peebles 1980;Martínez & Saar 2002). For galaxy filaments, the correlation function along the filament can be expressed in terms of the distances between the galaxies measured along the filament.…”

Section: Estimating the Pair Correlation Functionmentioning

confidence: 99%

Galaxy filaments as pearl necklaces

Tempel

Kipper

Saar

et al. 2014

A&A

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Context. Galaxies in the Universe form chains (filaments) that connect groups and clusters of galaxies. The filamentary network includes nearly half of the galaxies and is visually the most striking feature in cosmological maps. Aims. We study the distribution of galaxies along the filamentary network, trying to find specific patterns and regularities. Methods. Galaxy filaments are defined by the Bisous model, a marked point process with interactions. We use the two-point correlation function and the Rayleigh Z-squared statistic to study how galaxies and galaxy groups are distributed along the filaments. Results. We show that galaxies and groups are not uniformly distributed along filaments, but tend to form a regular pattern. The characteristic length of the pattern is around 7 h −1 Mpc. A slightly smaller characteristic length 4 h −1 Mpc can also be found, using the Z-squared statistic. Conclusions. We find that galaxy filaments in the Universe are like pearl necklaces, where the pearls are galaxy groups distributed more or less regularly along the filaments. We propose that this well-defined characteristic scale could be used to test various cosmological models and to probe environmental effects on the formation and evolution of galaxies.Key words. methods: numerical -methods: observational -large-scale structure of Universe IntroductionMany cosmological probes have been developed and used to estimate the parameters of the cosmological models describing our Universe. Most of them rely on some aspects of the large-scale structure. The most common probe used to quantify galaxy clustering is the two-point correlation function which was first used decades ago (Davis & Geller 1976;Groth & Peebles 1977;Davis et al. 1988;Hamilton 1988;White et al. 1988;Boerner et al. 1989;Einasto 1991) It is well known that galaxy filaments are visually the most dominant structures in the galaxy distribution, being part of the so-called cosmic network (Jõeveer et al. 1978;Bond et al. 1996). Presumably, nearly half (∼40%) of the galaxies (or mass in simulations) are located in filaments. This number is based on morphological or dynamical classification of the cosmic web (e.g. Jasche et al. 2010;Tempel et al. 2014b;Cautun et al. 2014). Properties of the three-point correlation function also indicate that galaxies tend to populate filamentary structures (Guo et al. 2014a) and, indeed, filaments have been found between galaxy clusters (e.g. Dietrich et al. 2012). Tempel et al. (2014a) show Appendices are available in electronic form at

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Section: Estimating the Pair Correlation Functionmentioning

confidence: 99%

Galaxy filaments as pearl necklaces

Tempel

Kipper

Saar

et al. 2014

A&A

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“…We use the co-moving distances (see, e.g. Martínez & Saar 2002) as the linear dimensions, calculated using the cosmological parameters listed above. The lower distance limit (55 h −1 Mpc) is chosen to exclude galaxies of the All the galaxy parameters used are given in Table 1 together with their SDSS CAS archive names.…”

Section: Galaxy Samplementioning

confidence: 99%

Galaxy morphology, luminosity, and environment in the SDSS DR7

Tempel

Saar

Liivamägi

et al. 2011

A&A

103

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Aims. We study the influence of the environment on the evolution of galaxies by investigating the luminosity function (LF) of galaxies of different morphological types and colours at different environmental density levels. Methods. We construct the LFs separately for galaxies of different morphology (spiral and elliptical) and of different colours (red and blue) using data from the Sloan Digital Sky Survey (SDSS), correcting the luminosities for the intrinsic absorption. We use the global luminosity density field to define different environments, and analyse the environmental dependence of galaxy morphology and colour. The smoothed bootstrap method is used to calculate confidence regions of the derived luminosity functions. Results. We find a strong environmental dependency for the LF of elliptical galaxies. The LF of spiral galaxies is almost environment independent, suggesting that spiral galaxy formation mechanisms are similar in different environments. Absorption by the intrinsic dust influences the bright-end of the LF of spiral galaxies. After attenuation correction, the brightest spiral galaxies are still about 0.5 mag less luminous than the brightest elliptical galaxies, except in the least dense environment, where spiral galaxies dominate the LF at every luminosity. Despite the extent of the SDSS survey, the influence of single rich superclusters is present in the galactic LF of the densest environment.

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“…Indeed, detailed N-body simulations of large scale structure show that filaments defining the cosmic web first form on the smallest scales. The scale-length characterizing the cosmic web grows as the universe expands, until at the present epoch the cosmic web consists of a fully developed supercluster-void network with a scale-length of several tens of Megaparsec [181,183,119,206].…”

Section: Dark Mattermentioning

confidence: 99%

5 Dark Matter and Dark Energy

Sahni¹

2004

Lecture Notes in Physics

494

287

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Abstract. I briefly review our current understanding of dark matter and dark energy. The first part of this paper focusses on issues pertaining to dark matter including observational evidence for its existence, current constraints and the 'abundance of substructure' and 'cuspy core' issues which arise in CDM. I also briefly describe MOND. The second part of this review focusses on dark energy. In this part I discuss the significance of the cosmological constant problem which leads to a predicted value of the cosmological constant which is almost 10 123 times larger than the observed value Λ/8πG ≃ 10 −47 GeV 4 . Setting Λ to this small value ensures that the acceleration of the universe is a fairly recent phenomenon giving rise to the 'cosmic coincidence' conundrum according to which we live during a special epoch when the density in matter and Λ are almost equal. Anthropic arguments are briefly discussed but more emphasis is placed upon dynamical dark energy models in which the equation of state is time dependent. These include Quintessence, Braneworld models, Chaplygin gas and Phantom energy. Model independent methods to determine the cosmic equation of state and the Statefinder diagnostic are also discussed. The Statefinder has the attractive property ... a /aH 3 = 1 for LCDM, which is helpful for differentiating between LCDM and rival dark energy models. The review ends with a brief discussion of the fate of the universe in dark energy models.

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Statistics of the Galaxy Distribution

Cited by 207 publications

References 0 publications

Galaxy filaments as pearl necklaces

Galaxy filaments as pearl necklaces

Galaxy morphology, luminosity, and environment in the SDSS DR7

5 Dark Matter and Dark Energy

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