Statistical properties of the spatial distribution of galaxies

Astrophysical Bulletin (Impact Factor: 0.87). 10/2009; 64(3):217-228. DOI: 10.1134/S199034130903002X
Source: arXiv

ABSTRACT The methods of determining the fractal dimension and irregularity scale in simulated galaxy catalogs and the application of
these methods to the data of the 2dF and 6dF catalogs are analyzed. Correlation methods are shown to be correctly applicable
to fractal structures only at the scale lengths from several average distances between the galaxies, and up to (10 − 20)%
of the radius of the largest sphere that fits completely inside the sample domain. Earlier the correlation methods were believed
to be applicable up to the entire radius of the sphere and the researchers did not take the above restriction into account
while finding the scale length corresponding to the transition to a uniform distribution. When an empirical formula is applied
for approximating the radial distributions in the samples confined by the limiting apparent magnitude, the deviation of the
true radial distribution from the approximating formula (but not the parameters of the best approximation) correlate with
fractal dimension. An analysis of the 2dF catalog yields a fractal dimension of 2.20 ± 0.25 on scale lengths from 2 to 20
Mpc, whereas no conclusive estimates can be derived by applying the conditional density method for larger scales due to the
inherent biases of the method. An analysis of the radial distributions of galaxies in the 2dF and 6dF catalogs revealed significant
irregularities on scale lengths of up to 70 Mpc. The magnitudes and sizes of these irregularities are consistent with the
fractal dimension estimate of D =2.1–2.4.

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    ABSTRACT: We present the reconstructed real-space density and the predicted velocity fields from the Two-Micron All-Sky Redshift Survey (2MRS). The 2MRS is the densest all-sky redshift survey to date and includes about 23 200 galaxies with extinction-corrected magnitudes brighter than Ks= 11.25. Our method is based on the expansion of these fields in Fourier–Bessel functions. Within this framework, the linear redshift distortions only affect the density field in the radial direction and can easily be deconvolved using a distortion matrix. Moreover, in this coordinate system, the velocity field is related to the density field by a simple linear transformation. The shot noise errors in the reconstructions are suppressed by means of a Wiener filter which yields a minimum variance estimate of the density and velocity fields. Using the reconstructed real-space density fields, we identify all major superclusters and voids. At 50 h−1 Mpc, our reconstructed velocity field indicates a backside infall to the Great Attractor region of vinfall= (491 ± 200) (β/0.5) km s−1 in the Local Group frame and vinfall= (64 ± 205) (β/0.5) km s−1 in the cosmic microwave background (CMB) frame and β is the redshift distortion parameter. The direction of the reconstructed dipole agrees well with the dipole derived by Erdoğdu et al. The misalignment between the reconstructed 2MRS and the CMB dipoles drops to 13° at around 5000 km s−1 but then increases at larger distances.
    Monthly Notices of the Royal Astronomical Society 11/2006; 373(1):45 - 64. DOI:10.1111/j.1365-2966.2006.11049.x · 5.11 Impact Factor
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    ABSTRACT: We present a new CCD survey of galaxies within the N and S strips of the 2dFGRS areas. We use the new CCD data to check the photographic photometry scales of the 2dFGRS, APMBGC, APM-Stromlo Redshift Survey, Durham-UKST (DUKST) survey, Millenium Galaxy Catalogue (MGC) and Sloan Digital Sky Survey (SDSS). We find evidence for scale and zero-point errors in the 2dFGRS northern field, DUKST and APM data of 0.10, 0.24 and 0.31 mag. respectively; we find excellent agreement with the MGC and SDSS photometry. We find conclusive evidence that the S counts with B<17 mag are down by ~30% relative to both the N counts and to the models of Metcalfe et al. We further compare the n(z) distributions from the B<17 mag. DUKST and B<19.5 2dFGRS redshift surveys using the corrected photometry. While the N n(z) from 2dFGRS appears relatively homogeneous over its whole range, the S n(z) shows a 30% deficiency out to z=0.1; at higher redshifts it agrees much better with the N n(z) and the homogeneous model n(z). The DUKST n(z) shows that the S `hole' extends over a 20 by 75 degree squared area. The troughs with z<0.1 in the DUKST n(z) appear deeper than for the fainter 2dFGRS data. This may be evidence that the local galaxy distribution is biased on >50 h-1 Mpc scales which is unexpected in a Lambda-CDM cosmology. Finally, since the Southern local void persists over the full area of the APM and APMBGC with a ~25% deficiency in the counts below B~17, this means that its extent is ~300 h-1 Mpc by 300 h-1 Mpc on the sky as well as ~300 h-1 Mpc in the redshift direction. Such a 25% deficiency extending over ~10^7 h-3 Mpc^3 may imply that the galaxy correlation function's power-law behaviour extends to \~150 h-1 Mpc with no break and show more excess large-scale power than detected in the 2dFGRS correlation function or expected in the Lambda-CDM cosmology. Comment: 15 pages, 17 figures
    Monthly Notices of the Royal Astronomical Society 02/2003; 354(4). DOI:10.1111/j.1365-2966.2004.08217.x · 5.11 Impact Factor
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    ABSTRACT: Using the bright galaxy counts from the 2 Micron All Sky Survey (2MASS) second incremental release, two techniques for probing large-scale structure at distances of ~150 h-1 Mpc are investigated. First, we study the counts from two sets of six 5 degree by ~80 degree strips in the two galactic caps. In the six southern strips a deficit of ~30% was found relative to a predicted homogeneous distribution at K~11. These strips were also in good agreement with a model incorporating the radial density function of the southern 2dF Galaxy Redshift Survey (2dFGRS), which shows a deep underdensity between ~90 and 180 h-1 mpc. These results indicate a very large `local hole' in the Southern Galactic Cap (SGC) to >150 h-1 Mpc with a linear size across the sky of ~200 h-1 Mpc, but with a significantly lower mean underdensity of ~30% than that suggested by the bright APM SGC counts. The counts in the northern set of strips are low overall but indicate a more varied pattern. When all the available 2MASS data with |b|>30 were aggregated, they indicated underdensities of ~18% and ~30% at K~11 for the northern and southern areas respectively. Our second method uses the ratio of the counts with 11.38<K<12.38 to 12.88<K<13.38 binned in 25 degree squared areas; the counts from these areas provide a smoothed map over the sky of the slope in the counts between K=11.38 and 13.38. The resulting map picks out known rich clusters, demonstrating usefulness as a probe of LSS at distances of <150 h-1 Mpc. Interestingly, the map also shows large regions, \~100 degrees across, of steep counts in both hemispheres. Thus, the present 2MASS data suggest the presence of a potentially huge contiguous void stretching from south to north, indicating the possible presence of significant power on scales of >300 h-1 Mpc in the galaxy power spectrum. Comment: 9 pages, 7 figures
    Monthly Notices of the Royal Astronomical Society 02/2003; 345(3). DOI:10.1046/j.1365-8711.2003.07027.x · 5.11 Impact Factor
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