Spatial Distribution Of Objects Research Articles

The field surrounding NGC 7603: Cosmological or non-cosmological redshifts?

We present new observations of the field surrounding the Seyfert galaxy NGC 7603, where four galaxies with different redshifts - NGC 7603 (z = 0.029), NGC 7603B (z = 0.057) and two fainter emission line galaxies (z = 0.245 and z = 0.394) - are apparently connected by a narrow filament, leading to a possible case of anomalous redshift. The observations comprise broad and narrow band imaging and intermediate resolution spectroscopy of some of the objects in the field. The new data confirm the redshift of the two emission-line objects found within the filament connecting NGC 7603 and NGC 7603B, and settles their type with better accuracy. Although both objects are point-like in ground based images, using HST archive images we show that the objects have structure with a FWHM = 0.3-0.4 arcsec. The photometry in the R-band obtained during three different campaigns spread over two years does not show any signs of variability in these objects above 0.3−0. 4m ag. All the above information and the relative strength and width of the main spectral lines allow us to classify these as HII galaxies with very vigorous star formation, while the rest of the filament and NGC 7603B lack star formation. We delineate the halo of NGC 7603 out to 26.2 mag/arcsec 2 in the Sloan r band filter and find evidence for strong internal distortions. New narrow emission line galaxies at z = 0.246, 0.117 and 0.401 are also found at respectively 0.8, 1.5 and 1.7 arcmin to the West of the filament within the fainter contour of this halo. We have studied the spatial distribution of objects in the field within 1.5 arcmin of NGC 7603. We conclude that the density of QSOs is roughly within the expected value of the limiting magnitude of our observations. However, the configuration of the four galaxies apparently connected by the filament appears highly unusual. The probability of three background galaxies of any type with apparent B-magnitudes up to 16.6, 21.1 and 22.1 (the observed magnitudes, extinction correction included) being randomly projected on the filament of the fourth galaxy (NGC 7603) is ≈3 × 10 −9 . Furthermore, the possible detection of very vigorous star formation observed in the HII galaxies of the filament would have a low probability if they were background normal-giant galaxies; instead, the intensity of the lines is typical of dwarf HII galaxies. Hence, a set of coincidences with a very low probability would be necessary to explain this as a fortuitous projection of background sources. Several explanations in terms of cosmological or non-cosmological redshifts are discussed.

Image analysis in physics–sensitivity analysis of morphological methods and their application in thin film physics

In the contribution, several morphological algorithms for the description of spatial distribution of objects are analysed, the one-number features suggested and tested by means of computer experiment. A special attention was devoted to the description of system arrangement by means of Wigner-Seitz cells. It was found that for all morphological methods, it is possible to derive numerical features and some of them can be used in the study of thin film growth. The best features proved to be the features derived from radial distribution function and from areas of Wigner-Seitz cells.

On the role of spatial stochastic models in understanding landscape indices in ecology

Spatial stochastic models play an important role in understanding and predicting the behaviour of complex systems. Such models may be implemented with explicit knowledge of only a limited number of parameters relating to spatial relationships among locations. Consequently, they are often used instead of deterministic‐mechanistic models, which may potentially require an unrealistically large number of parameters. Currently, in contrast to spatial stochastic models, the parameterization of the joint spatial distribution of objects in landscape models is more often implicit than explicit. Here, we investigate the similarities and differences between bona fide spatial stochastic models and landscape models by focusing mostly on the relationships between processes, their realizations (patterns), representation and measurement, and their use in exploratory as well as confirmatory data analysis. One of the most important outcomes of recognizing the importance of stochastic processes is the acknowledgement that the spatial pattern observed in a landscape is only one realization of that process. Hence, while ecologists have been using landscape pattern indices (LPIs) to characterize landscape heterogeneity and/or make inferences about processes shaping the landscape, no stochastic modelling framework has been developed for their proper statistical elucidation. Consequently, several (mis)uses of LPIs draw conclusions about landscapes which are suspect. We show that several reports about sensitivities of LPIs to measurements have common roots that can be made explicitly manageable by adopting stochastic models of spatial structure. The key parameters of these stochastic models are composition and configuration, which, in general, cannot be estimated independently from each other. We outline how to develop the stochastic framework to interpret observations and make some recommendations to practitioners about everyday usage. The conceptual linkages between patterns and processes are particularly important in light of recent efforts to bridge the static‐structural and the dynamic‐analytic traditions of ecology.

An Analytical Approach to Inhomogeneous Structure Formation

We develop an analytical formalism that is suitable for studying inhomogeneous structure formation, by studying the joint statistics of dark matter halos forming at two points. Extending the Bond et al. (1991) derivation of the mass function of virialized halos, based on excursion sets, we derive an approximate analytical expression for the ``bivariate'' mass function of halos forming at two redshifts and separated by a fixed comoving Lagrangian distance. Our approach also leads to a self-consistent expression for the nonlinear biasing and correlation function of halos, generalizing a number of previous results including those by Kaiser (1984) and Mo & White (1996). We compare our approximate solutions to exact numerical results within the excursion-set framework and find them to be consistent to within 2% over a wide range of parameters. Our formalism can be used to study various feedback effects during galaxy formation analytically, as well as to simply construct observable quantities dependent on the spatial distribution of objects. A code that implements our method is publicly available at this http URL

Spatial distribution of galactic halos and their merger histories

We use a novel statistical tool, the mark correlation functions (MCFs), to study clustering of galaxy- size halos as a function of their properties and environment in a high-resolution numerical simulation of the CDM cosmology. We applied MCFs using several types of continuous and discrete marks: maximum circular velocity of halos, merger mark indicating whether halos experienced or not a major merger in their evolution history (the marks for halo with mergers are further split according to the epoch of the last major merger), and a stripping mark indicating whether the halo underwent a tidal stripping (i.e., mass loss). We nd that halos which experienced a relatively early ( z> 1) major merger or mass loss (due to tidal stripping) in their evolution histories are over-abundant in halo pairs with separations <3 h 1 Mpc. This result can be interpreted as spatial segregation of halos with dierent merger histories, qualitatively similar to the morphological segregation in the observed galaxy distribution. In addition, we nd that at z = 0 the mean circular velocity of halos in pairs of halos with separations <10 h 1 Mpc is larger than the mean circular velocity vcirc of the parent halo sample. This mean circular velocity enhancement increases steadily during the evolution of halos from z =3t oz = 0, and indicates that the luminosity dependence of galaxy clustering may be due to the mass segregation of galactic dark matter halos. The analysis presented in this paper demonstrate that MCFs provide powerful, yet algorithmically simple, quantitative measures of segregation in the spatial distribution of objects with respect to their various properties (marks). This should make MCFs very useful for analysis of spatial clustering and segregation in current and future large redshift surveys.

Is a Power-Law Form of the Correlation Gamma Function Sufficient to State that a Distribution Has Fractal Properties?

This investigation indicates an ambiguity in interpreting the results of applying the apparatus of the correlation gamma function [Γ(r) and Γ*(r)] to analyze the spatial distribution of objects from some sample. The presence of a linear section in the dependences of log(Γ) on log(r) and of log(Γ*) on log(r) proves to be insufficient to state that the distribution has fractal properties (self-similarity). It is shown that a change in the geometrical boundaries of the sample may influence the form of the dependences of log(Γ) on log(r) and of log(Γ*) on log(r).

Study of spatial distribution of objects in composite films

A computer experiment was suggested for testing suitable methods for morphological analysis. Two computer models were prepared to study the possibility of at least partial reconstruction of 3D structure from their 2D projections or sections. The importance of some morphological characteristics and their review is shown in the paper.

Applying the golden rule of sampling for query estimation

Query size estimation is crucial for many database system components. In particular, query optimizers need efficient and accurate query size estimation when deciding among alternative query plans. In this paper we propose a novel sampling technique based on the golden rule of sampling, introduced by von Neumann in 1947, for estimating range queries. The proposed technique randomly samples the frequency domain using the cumulative frequency distribution and yields good estimates without any a priori knowledge of the actual underlying distribution of spatial objects. We show experimentally that the proposed sampling technique gives smaller approximation error than the Min-Skew histogram based and wavelet based approaches for both synthetic and real datasets. Moreover, the proposed technique can be easily extended for higher dimensional datasets.

Morphological Characteristics of Composite Films

For the testing of methods for morphological analysis of composite films, a computer experiment was suggested. Two models were prepared to study the possibility of at least partial reconstruction of 3D structures from their 2D projections or sections. The importance of some morphological characteristics for the reconstruction of size and/or spatial distribution of objects is shown in the paper. It illustrates the usage and significance of the integral transform method for the unfolding of the structures, too.

Statistical methods for analyzing the distribution of spatial objects in relation to a surface

This paper develops statistical methods for analyzing the distribution of spatial objects—points, convex polygons, and line segments—in relation to a surface. We propose statistics for measuring the relationship between the distribution of these objects and a surface and derive their expectations and variances under the null hypothesis that the objects are independently and randomly distributed. The statistics are approximately distributed according to the normal distribution under the null hypothesis, which enables us to test the significance of the spatial relationships statistically. Using the proposed methods, we empirically analyze the distribution of convenience stores in relation to the distribution of population in a suburb of Osaka, Japan. Some empirical findings are shown.

Errors in Areal Weighting Interpolation between Incompatible Zonal Systems

Map overlay operation in GIS is often followed by a data transfer between incompatible zonal systems. There are various methods of data transfer which are called areal interpolation methods. Any interpolation methods, however, involve error in data transfer because of insufficient information about the distribution of spatial objects in overlaid zones. This paper proposes a probabilistic model of the error in count data transferred through the areal weighting method, and analyze the relationship among the source zonal system, target zone, and the distribution of spatial objects whose counts are recorded in GIS. Both theoretical and empirical findings are shows.

Computer simulation of semicontinuous and continuous metal film morphology

The methods convenient for the morphological analysis of very thin metal films are analysed by the computer simulation technique. An attempt is made to extend the range of validity of methods developed for the study of discontinuous films using these methods to describe both structures with irregular objects and thicker semicontinuous and continuous structures. It was found that the covariance function, one of the basic methods for the characterisation of spatial distribution of objects in discontinuous metal films, is a convenient approach even in the case when other simple morphological methods cannot be used at all. In order to derive the physical meaning of the information obtained from the covariance curves a computer experiment based on four models in three modifications for discontinuous, semicontinuous and continuous structures was performed.

Morphological analysis of discontinuous and semicontinuous metal films

In the paper, the morphology of discontinuous metal films with irregular islands and of semicontinuous metal films is studied by the combination of computer experiment and analysis of film micrographs. In order to determine the physical interpretation of derived morphological characteristics, four models in two modifications for both discontinuous and semicontinuous metal films were prepared. These models were analysed by the standard morphological algorithms for description of spatial distribution of objects and the physical meaning of these characteristics for irregular objects was discussed. It was found that although the sensitivity of methods used decreases with increasing film thickness, the covariance method is the most promising of them.

Extreme Microlensing toward the Galactic Bulge

Extreme microlensing events, defined as events with maximum magnification Amax ≳ 200, are a potentially powerful probe of the mass spectrum and spatial distribution of objects along lines of sight toward the Galactic bulge. About 30 yr-1 such events are expected for main-sequence sources with I0 < 19. For many of these it is possible to measure both a "proper motion" and a "parallax," that together would yield individual mass, distance, and transverse-speed determinations of the lensing object. The proper motion is determined from finite-source effects when the lens transits, or nearly transits, the source. The parallax is determined by observing the difference in the light curve as seen from two Earth observatories separated by about 1 Earth radius, R⊕. The size of the parallax effect is ~Amax R⊕/e, where e is the projected Einstein radius and can be of order 1%. Detection of candidate events requires a pixel-lensing search of the entire bulge once per day, preferably by at least two observatories on different continents. Follow-up observation must be carried out using optical/infrared photometry, with short (e.g., 1 minute) exposures on small ( ≳ 1 m) telescopes. Extreme microlensing observations toward the Large Magellanic Cloud do not appear feasible at the present time.

Nearest-Neighbor Analysis of Spatial Point Patterns: Application to Biomedical Image Interpretation

Analysis of the spatial distributions of objects is fundamental to biomedical image interpretation. Nearest-neighbor (NN) methods are generally used to assess whether objects are arranged at random or in a deterministic manner. Simple standard NN techniques, however, may fail to identify complex spatial organizations. To overcome this problem the present study proposes a NN iterative algorithm that enables deterministic spatial patterns to be detected by identifying the distances between objects for which there is the greatest deviation from randomness and hence the amplitude of the areas of maximum reciprocal influence between objects. The performance of the algorithm is evaluated by applying it to both manufactured and experimental data. The manufactured data example showed that the proposed procedure produced neither false positives or negatives. The method proved to be extremely sensitive, detecting even small deviations from randomness. The experimental analysis was applied to the study of the spatial distribution of apoptotic structures in malignant neoplastic tissue. It showed that the apoptotic cells and bodies are characterized by a complex spatial pattern, and aggregate closely.

A Wavelet Space-Scale Decomposition Analysis of Structures and Evolution of QSO LY alpha Absorption Lines

A wavelet space-scale decomposition (SSD) analysis of large scale structures in the universe has been developed. The SSD method of identifying and measuring structures in the spatial distribution of objects has been demonstrated. The position and strength (richness) of the identified clusters can be described by the corresponding coefficient of the wavelet transform. Using this technique, we systematically detected the clustering and its evolution of QSO's Ly$\alpha$ forest lines in real data and simulated samples. We showed that the clusters of Ly$\alpha$ absorbers do exist on scales as large as at least 20 h$^{-1}$ Mpc at significance levels of 2-4 $\sigma$. Independent data sets show about the same strength distribution of the decomposed clusters. The number densities of the clusters on scales of 10 - 20 h$^{-1}$ Mpc are found to evolve in an opposite sense as that of the lines themselves, i.e. they decrease with redshift. We also showed that the number density and the strength distribution of clusters can play an important role in testing or discriminating models, i.e. it can distinguish real data and simulated samples, which cannot be discriminated by traditional ways. We used Daubechies 4 and Mallat wavelets as the bases of the SSD. All above-mentioned conclusions do not depend on either wavelet basis.

Effect of Terrain Shape and Object Grouping on Detection of Altitude Change in a Flight Simulator

Multidimensional scaling (MDS) analyses of flight simulator visual scenes reveal that both the shape of the terrain surface as well as the spatial distribution of objects on the terrain are salient to pilots flying at low altitudes. MDS is based upon similarity ratings and it was deemed important to verify the relevance of these scene properties using a performance based task in a flight simulator. The task was an ascent/descent discrimination task similar to that used in other flight simulation research. Terrain shape and elements on the terrain (texture and objects) were factorially manipulated. Presence of hills as well as the spatial organization of objects on the terrain affected performance in some conditions. A positive effect of hills is noteworthy because hills did not extend above the horizon and therefore posed no vertical obstructions. Thus, they provide relevant information for perceiving altitude change apart from the role they may play in obstructing vision or navigation.

Generalized associated point methods for sampling planar objects

SUMMARYFor estimation of the mean number of objects per unit area from observations in a bounded region (sampling window) T in the plane, a generalized associated point method is discussed. By this method, m points are associated with each object, and an object with k associated points inside T is counted with weight k/m. A general formula for the variance of the estimator is derived and explicit expressions are given for Poisson and hard‐core models for the spatial distribution of objects in the plane.

The archeology of trade

Contemporary archaeologists are well aware that trade constitutes only one form of ex? change. Material goods may be distributed by the exchange of gifts between rulers or entire societies, tribute payments, piracy and brig? andage, or through marriage alliances. Such a list obviously could be extended, and the realization of this has led historian Philip Grierson to conclude that the "very nature [of the archaeological evidence] substitutes inference for explanation;. . . the spade can? not lie, but it owes this merit in part to the fact that it cannot speak."1 One cannot satis? factorily answer such a criticism by a simple recitation of the now familiar archaeological credo that cultural behavior is patterned and that these patterns, which are reflected in materi ? culture, can be deduced through the formulation and testing of alternative hypoth? eses. Rather, we must first ask how archaeol? ogists have traditionally distinguished between trade and other means of spatially distributing material goods. We will evaluate three approaches and then consider how best to relate the de? termination of trade, a particular form of ex? change, to the broader question of its effects on the societies participating in the trading network. A cursory review of the archaeological literature quickly makes it clear that the distinction between trade and other forms of exchange has never been systematically for? mulated. The first and most common approach has been to ignore the problem altogether. The spatial distribution of objects is studied to evaluate such alternative explanations of cultural contact as trade, political conquest, and migration. If there is no evidence of destruction or of a sloping chronological horizon, if the material is foreign, if sufficient quantity exists, and if the similarities are exact, then this "contact" is explained as trade. From this perspective, trade is simply a peaceful form of exchange which does not in? volve the permanent displacement of peoples or cultures; no distinction is made between trade, particularly the organized form that is con? trolled and directed by an institutionalized class of merchants, and other types of exchange, such as the reciprocal presentation of gifts. The second approach proceeds further by showing that the widespread distribution of archaeological material is consistent with patterns known from the anthropological literature. The judicious use of ethnographic analogies can of course be illuminating, but it would be incorrect to view it as a form of ex? planation. This approach frequently proceeds as follows: (1) the presentation of a distribu? tion; (2) the admission of ignorance as to the mechanics and organization of the form of ex? change responsible for the distribution; and (3) a speculative but commonsense reconstruc? tion based on ethnographic analogies that are hopefully appropriate. This is the procedure followed by Graham Clark in his discussion of the trade in finished flint blades, stone axes, and adzes in late Mesolithic?early Neo? lithic Northwest Europe.2 If we were to accept the traditional versus Philip L. Kohl is Associate Professor of Anthropology, Wellesley College, Massachusetts.