On the fractal structure of the visible universe (original) (raw)

Is the Universe a fractal? Results from the Southern Sky Redshift Survey 2

Astronomy & Astrophysics, 1998

We perform a fractal analysis of the Southern Sky Redshift Survey 2, following the methods prescribed by Pietronero and collaborators, to check their claim that the galaxy distribution is fractal at all scales, and we discuss and explain the reasons of some controversial points, through tests on both galaxy samples and simulations. We confirm that the amplitude of the two-point

Is the Universe a fractal? Results from the SSRS2

1998

We perform a fractal analysis of the Southern Sky Redshift Survey 2, following the methods prescribed by Pietronero and collaborators, to check their claim that the galaxy distribution is fractal at all scales, and we discuss and explain the reasons of some controversial points, through tests on both galaxy samples and simulations. We confirm that the amplitude of the two-point correlation function does not depend on the sample depth, but increases with luminosity. We find that there is no contradiction between the results of standard and non-standard statistical analysis; moreover, such results are consistent with theoretical predictions derived from standard CDM models of galaxy formation, and with the hypothesis of homogeneity at large scale ($\sim 100$ \h). However, for our SSRS2 volume-limited subsamples we show that the first zero-point of the autocorrelation function xi(s)\xi(s)xi(s) increases linearly with the sample depth, and that its value is comparable to the radius of the maxim...

Fractal analysis of the galaxy distribution in the redshift range 0.45 < z < 5.0

Evidence is presented that the galaxy distribution can be described as a fractal system in the redshift range of the FDF galaxy survey. The fractal dimension D was derived using the FDF galaxy volume number densities in the spatially homogeneous standard cosmological model with Ωm0=0.3, ΩΛ0=0.7 and H0=70kms−1Mpc−1. The ratio between the differential and integral number densities γ and γ∗ obtained from the red and blue FDF galaxies provides a direct method to estimate D, implying that γ and γ∗ vary as power-laws with the cosmological distances. The luminosity distance dL, galaxy area distance dG and redshift distance dz were plotted against their respective number densities to calculate D by linear fitting. It was found that the FDF galaxy distribution is characterized by two single fractal dimensions at successive distance ranges. Two straight lines were fitted to the data, whose slopes change at z≈1.3 or z≈1.9 depending on the chosen cosmological distance. The average fractal dimension calculated using γ∗ changes from ⟨D⟩=1.4+0.7−0.6 to ⟨D⟩=0.5+1.2−0.4 for all galaxies, and D decreases as z increases. Small values of D at high z mean that in the past galaxies were distributed much more sparsely and the large-scale galaxy structure was then possibly dominated by voids. Results of Iribarrem et al. (2014, arXiv:1401.6572) indicating similar fractal features with ⟨D⟩=0.6±0.1 in the far-infrared sources of the Herschel/PACS evolutionary probe (PEP) at 1.5≲z≲3.2 are also mentioned.

Galaxy distributions as fractal systems

The European Physical Journal C

This paper discusses if large scale galaxy distribution samples containing almost one million objects can be characterized as fractal systems. The analysis performed by Teles et al. (Phys Lett B 813:136034, 2021) on the UltraVISTA DR1 survey is extended here to the SPLASH and COSMOS2015 catalogs, hence adding 750k new galaxies with measured redshifts to the studied samples. The standard \Lambda ΛCDMcosmologyhavingΛ CDM cosmology havingΛCDMcosmologyhavingH_0=(70\pm 5)H0=(70±5)km/s/MpcandnumberdensitytoolsrequiredfordescribingthesegalaxydistributionsassinglefractalsystemswithdimensionDareadopted.WeusetheluminositydistanceH 0 = ( 70 ± 5 ) km/s/Mpc and number density tools required for describing these galaxy distributions as single fractal systems with dimension D are adopted. We use the luminosity distanceH0=(70±5)km/s/MpcandnumberdensitytoolsrequiredfordescribingthesegalaxydistributionsassinglefractalsystemswithdimensionDareadopted.Weusetheluminositydistanced_{\scriptscriptstyle L}dL,redshiftdistanced L , redshift distancedL,redshiftdistanced_zdzandgalaxyareadistance(transversecomovingdistance)d z and galaxy area distance (transverse comoving distance)dzandgalaxyareadistance(transversecomovingdistance)d_{\scriptscriptstyle G}dGasrelativisticdistancedefinitionstoderivegalaxynumberdensitiesintheredshiftintervald G as relativistic distance definitions to derive galaxy number densities in the redshift intervaldGasrelativisticdistancedefinitionstoderivegalaxynumberdensitiesintheredshiftinterval0.1\le z\le 4$$ 0.1 ≤ z ≤ 4 at volume limited subsamples defined by absolute magnitudes in the K-band. Similar t...