Mapping the Universe

Geller, Margaret J.; Huchra, J. P.

doi:10.1126/science.246.4932.897

Cited by 776 publications

(627 citation statements)

References 34 publications

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“…From Eq.5 that the difference between the apparent and the absolute magnitudes of an object at distance r is (at relatively small distances, neglecting relativistic effects) m − M = 5 log 10 r + 25 (8) where r is expressed in Megaparsec (1Mpc = 3.26 · 10 6 light years. )…”

Section: Galaxy Number Counts: Basic Relationsmentioning

confidence: 99%

“…We report in Table 1 the minimal statistical lengths for several redshift surveys [5], [7], [8] - [15], [58]- [61], some of which are published, while others are in progress, and this provides a precise prediction that can be tested in these surveys. We have tested such a condition in Perseus-Pisces, CfA1, LEDA and ESP and the agreement is very good.…”

Section: Experimental Implicationsmentioning

confidence: 99%

“…These results can be useful also to design future programs for redshift or angular surveys. On this basis we can predict the expected statistical properties of several surveys such as CfA2 [8], Las Campanas [12], ESP [15], etc.…”

Section: Introductionmentioning

confidence: 99%

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Finite size effects on the galaxy number counts: Evidence for fractal behavior up to the deepest scale

Labini

Gabrielli

Montuori

et al. 1996

Physica A: Statistical Mechanics and its Applications

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We introduce and study two new concepts which are essential for the quantitative analysis of the statistical quality of the available galaxy samples. These are the dilution effect and the small scale fluctuations. We show that the various data that are considered as pointing to a homogenous distribution are all affected by these spurious effects and their interpretation should be completely changed. In particular, we show that finite size effects strongly affect the determination of the galaxy number counts, namely the number versus magnitude relation (N (< m)) as computed from the origin. When one computes N (< m) averaged over all the points of a redshift survey one observes an exponent α = D/5 ≈ 0.4 compatible with the fractal dimension D ≈ 2 derived from the full correlation analysis. Instead the observation of an exponent α ≈ 0.6 at relatively small scales, where the distribution is certainly not homogeneous, is shown to be related to finite size effects. We conclude therefore that the observed counts correspond to a fractal distribution with dimension D ≈ 2 in the entire range 12 ∼ < m ∼ < 28, that is to say the largest scales ever probed for luminous matter. In addition our results permit to clarify various problems of the angular catalogs, and to show their compatibility with the fractal behavior. We consider also the distribution of Radio-galaxies, Quasars and γ ray burst, and we show their compatibility with a fractal structure with D ≈ 1.6 ÷ 1.8. Finally we have established a quantitative criterion that allows us to define and predict the statistical validity of a galaxy catalog (angular or three dimensional).

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Section: Galaxy Number Counts: Basic Relationsmentioning

confidence: 99%

Section: Experimental Implicationsmentioning

confidence: 99%

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Finite size effects on the galaxy number counts: Evidence for fractal behavior up to the deepest scale

Labini

Gabrielli

Montuori

et al. 1996

Physica A: Statistical Mechanics and its Applications

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“…The first observational evidence of giant voids was obtained more than 30 years ago (Joeveer et al 1978;Gregory & Thompson 1978). However, their systematic and quantitative study came later with the advent of the first large spectroscopic surveys (Huchra et al 1988;Geller & Huchra 1989;Bahcall 1995). Now it is well established that void sizes span a wide range of scales, from minivoids with diameters of about 3-5 Mpc in the Local Universe (Tikhonov & Karachentsev 2006) to the supervoids with diameters of about 200 Mpc (Lindner et al…”

Section: Introductionmentioning

confidence: 99%

Cosmic voids detection without density measurements

Elyiv

Marulli

Pollina

et al. 2015

Monthly Notices of the Royal Astronomical Society

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Cosmic voids are effective cosmological probes to discriminate among competing world models. Their identification is generally based on density or geometry criteria that, because of their very nature, are prone to shot noise. We propose two void finders that are based on dynamical criterion to select voids in Lagrangian coordinates and minimise the impact of sparse sampling. The first approach exploits the Zel'dovich approximation to trace back in time the orbits of galaxies located in voids and their surroundings, the second uses the observed galaxy-galaxy correlation function to relax the objects' spatial distribution to homogeneity and isotropy. In both cases voids are defined as regions of the negative velocity divergence, that can be regarded as sinks of the back-in-time streamlines of the mass tracers. To assess the performance of our methods we used a dark matter halo mock catalogue CoDECS, and compared the results with those obtained with the ZOBOV void finder. We find that the void divergence profiles are less scattered than the density ones and, therefore, their stacking constitutes a more accurate cosmological probe. The significance of the divergence signal in the central part of voids obtained from both our finders is 60% higher than for overdensity profiles in the ZOBOV case. The ellipticity of the stacked void measured in the divergence field is closer to unity, as expected, than what is found when using halo positions. Therefore our void finders are complementary to the existing methods, that should contribute to improve the accuracy of void-based cosmological tests.

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“…Approximately fifty-four 45'x45' fields were imaged during that time, resulting in a total of 27 degrees 2 of sky being imaged. The fields covered both the Pegasus and Cancer sky regions as well as the area around various (known) galaxies distributed in the Great Wall (Geller & Huchra 1989;Dell Antonio, Geller, & Bothun 1996). Six to eight flat field images were taken each night for each filter and were (median) combined to obtain the flat field images for that night's data.…”

Section: The Datamentioning

confidence: 99%

The Discovery of Red Low Surface Brightness Galaxies

O'Neil¹

1999

International Astronomical Union Colloquium

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Abstract. We have performed a digital survey for Low Surface Brightness (LSB) galaxies in the spiral-rich Cancer and Pegasus clusters as well as the low density regime defined by the Great Wall. A total of 127 galaxies were found with /xs(0) > 22.0 mag arcsec -2 , 119 of which were previously unidentified.Consistent with other surveys, we find a significant number of galaxies with /is(0) > 23.0 mag arcsec -2 which suggests that the space density of galaxies as a function of /^s(O) is not strongly peaked. To more rigorously test this hypothesis we compare the actual surface brightness distribution from our survey with that from two different types of Monte-Carlo based sky images and show that it is not possible to distinguish between the flat distribution and the Gaussian one as the proper description of the underlying surface brightness distribution for this survey beyond 24.0 mag arcsec -2 .The colors of the survey galaxies range continuously from very blue to the first discovery of very red LSB galaxies. It also includes a group of old galaxies which show evidence for recent star formation. This continuous range of colors clearly shows that LSB galaxies at the present epoch define a wide range of evolutionary states.

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Mapping the Universe

Cited by 776 publications

References 34 publications

Finite size effects on the galaxy number counts: Evidence for fractal behavior up to the deepest scale

Finite size effects on the galaxy number counts: Evidence for fractal behavior up to the deepest scale

Cosmic voids detection without density measurements

The Discovery of Red Low Surface Brightness Galaxies

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