Nearby Optical Galaxies: Selection of the Sample and Identification of Groups

In this paper we describe the Nearby Optical Galaxy (NOG) sample, which is a complete, distance-limited ($cz\leq$6000 km/s) and magnitude-limited (B$\leq$14) sample of $\sim$7000 optical galaxies. The sample covers 2/3 (8.27 sr) of the sky ($|b|>20^{\circ}$) and appears to have a good completeness in redshift (98%). We select the sample on the basis of homogenized corrected total blue magnitudes in order to minimize systematic effects in galaxy sampling. We identify the groups in this sample by means of both the hierarchical and the percolation {\it friends of friends} methods. The resulting catalogs of loose groups appear to be similar and are among the largest catalogs of groups presently available. Most of the NOG galaxies ($\sim$60%) are found to be members of galaxy pairs ($\sim$580 pairs for a total of $\sim$15% of objects) or groups with at least three members ($\sim$500 groups for a total of $\sim$45% of objects). About 40% of galaxies are left ungrouped (field galaxies). We illustrate the main features of the NOG galaxy distribution. Compared to previous optical and IRAS galaxy samples, the NOG provides a denser sampling of the galaxy distribution in the nearby universe. Given its large sky coverage, the identification of groups, and its high-density sampling, the NOG is suited for the analysis of the galaxy density field of the nearby universe, especially on small scales

SFI++ II: A New I-band Tully-Fisher Catalog, Derivation of Peculiar Velocities and Dataset Properties

We present the SFI++ dataset, a homogeneously derived catalog of photometric and rotational properties and the Tully-Fisher distances and peculiar velocities derived from them. We make use of digital optical images, optical long-slit spectra, and global HI line profiles to extract parameters of relevance to disk scaling relations, incorporating several previously published datasets as well as a new photometric sample of some 2000 objects. According to the completeness of available redshift samples over the sky area, we exploit both a modified percolation algorithm and the Voronoi-Delaunay method to assign individual galaxies to groups as well as clusters, thereby reducing scatter introduced by local orbital motions. We also provide corrections to the peculiar velocities for both homogeneous and inhomogeneous Malmquist bias, making use of the 2MASS Redshift Survey density field to approximate large scale structure. We summarize the sample selection criteria, corrections made to raw observational parameters, the grouping techniques, and our procedure for deriving peculiar velocities. The final SFI++ peculiar velocity catalog of 4861 field and cluster galaxies is large enough to permit the study not just of the global statistics of large scale flows but also of the {\it details} of the local velocity field.Comment: 14 pages, 6 figures, 4 external online tables, accepted for publication in ApJ

Geometrical tests of cosmological models. II. Calibration of rotational widths and disc scaling relations

This series of papers is dedicated to a new technique to select galaxies that can act as standard rods and standard candles in order to perform geometrical tests on large samples of high redshift galaxies to constrain different cosmological parameters. The goals of this paper are (1) to compare different rotation indicators in order to understand the relation between rotation velocities extracted from observations of the Halpha line and the [OII]3727 line, and (2) determine the scaling relations between physical size, surface brightness and magnitude of galaxies and their rotation velocity using the SFI++, a large catalog of nearby galaxies observed at I-band. A good correlation is observed between the rotation curve-derived velocities of the Halpha and [OII] observations, as well as between those calculated from velocity histograms, justifying the direct comparison of velocities measured from Halpha rotation curves in nearby galaxies and from [OII] line widths at higher redshifts. To provide calibration for the geometrical tests, we give expressions for the different scaling relations between properties of galaxies (size, surface brightness, magnitude) and their rotation speeds. Apart from the Tully-Fisher relation, we derive the size-rotation velocity and surface brightness-rotation velocity relations with unprecedentedly small scatters. We show how the best size-rotation velocity relation is derived when size is estimated not from disc scale lengths but from the isophotal diameter r23.5, once these have been corrected for inclination and extinction effects.Comment: 14 pages and 10 figures. A&A submitte

STUDY OF CHEMICAL AND MOLECULAR INFORMATION RELATED TO NIR AND IR SPECTROSCOPIC DATA FOR DAIRY SECTOR

In the last decades, the spectroscopic techniques have acquired reliability, since they are sufficiently accurate and precise for analysis of the macro-composition of food. In this work, NIR and IR techniques were applied to study some aspects of cow milk casein and fat globules. In dairy field, casein amount and quality have great influence on milk rennet properties and cheese yield. Caseins from milk of ruminants have been extensively studied, but the exact structure of the casein micelle is still debated. The research activity was addressed to verify the ability of spectroscopic techniques in the evaluation of modifications of casein fractions and sub-fractions as a function of pH and temperature. The NIRS ability in predicting casein fractions content and in detecting bonds involved in the micelle complex were also evaluated. The study was carried out on both commercial preparations of casein fractions and reconstituted casein samples. These were obtained by ultracentrifugation (native casein) and by precipitation at the iso-electric pH (acid casein) of individual milk samples, collected during two months periods in the Austria\u2019s region. The IR spectra of commercial caseins showed the phosphate band at 1100 cm-1, confirming its role in the stabilization of casein micelle structure. When NIR casein spectra were measured as a function of temperature, exclusively changes in water bands were detected, while regarding pH, Absorbance differences from the mean spectrum evidenced some modifications of linearity due to the number of negative charged amino acid residues at pH > 6.80 in the casein sub-fractions. Casein fractions content of reconstituted samples was determined by Capillary Zone Electrophoresis analyses. PLS analyses, performed with electrophoretic and NIR data, revealed the NIRS ability to determine and quantify casein genetic variants useful for milk selection for its final purpose. Moreover, the PCA analysis on the same samples proved the NIRS ability also to discriminate between samples obtained by physical and chemical treatments and to detect bonds involved in the micelle structure, especially phosphate group and its binding to calcium. FT-NIR spectroscopy was also applied to study the size distribution of fat globules: an aspect influencing the technological and sensorial milk characteristics. In this contest, the variability in the distribution of fat globules within cow breedings in Lombardy was studied during two years period. The reference particle size analyses of fat globules were performed using a granulometer. The Sauter Mean Diameter (SMD) was chosen as the best descriptor of particle size distribution. This parameter resulted to be more influenced by genetic factors than seasonal aspects. The differences among farms could be determinant in planning the milk collection for the technological destination, while the differences among the breeding bulls can be used for the animals\u2019 selection. Despite the importance of this parameter in several dairy processes, instrumentation for particle size analysis are not available in dairy laboratories. NIR instrumentation, instead, is largely used in dairy labs. NIR spectrum of whole milk arises from absorbance due to both molecular vibrations and elastic scattering related to the presence of fat globules in emulsion. Moreover, the amount of scattered photons depends on their size and wavelength. A rapid and economic method for estimating the distribution of fat globules in milk through a physical-mathematical model based on the study of the scattering component in the NIR spectrum was developed. The model, working in Visual Basic for Excel, calculates the optical density produced by milk fat globules, given the fat concentration. On the basis of the Weibull distribution, the model calculates the amount of globules with a certain diameter range, returning a first distribution curve. After the generation of a theoretical NIR spectrum, the model inversion was performed by minimizing the sum of squared differences between measured and theoretical spectra. At the end of the process, the new distribution curve was given. The performances of the model was tested by analyzing an external data set with both NIR and reference diffractometric data. For the SMD a very high coefficient of determination in prediction was found. In order to improve the applicability of the model, the use of a portable spectrometer for estimating the distribution of milk fat globules was evaluated trough standardization to bench-top instrument spectra. The calculation of milk fat globules diameter by a portable instrument standardized spectra through the mathematical model, gave comparable results with those calculated on master spectra

Measuring the Cosmic Equation of State with Galaxy Clusters in the DEEP2 Redshift Survey

The abundances of groups and clusters of galaxies are expected to have changed substantially since high redshift, with the strength of this evolution dependent upon fundamental cosmological parameters. Upcoming large redshift surveys of distant galaxies will make it possible to measure these quantities at z~1; when combined with the results of local redshift surveys currently underway, the evolution of cluster abundances may be determined. The DEEP2 Redshift Survey, planned to begin in Spring 2002, is particularly well-suited for this work because of the high spectroscopic resolution to be used; velocity dispersions of groups will be readily measurable. In this paper, we determine the constraints on dark energy models that counts of DEEP2 clusters should provide. We find that comparing cosmological models using the simultaneous distribution of clusters in both velocity dispersion and redshift yields significantly stronger constraints than the redshift distribution alone. The method can be made more powerful by employing a value of the fluctuation amplitude sigma_8 determined with upcoming techniques (external to DEEP2) that have no Omega_m degeneracy. The equation-of-state parameter for dark energy models, w=P/rho, can then be measured to ~0.1 from observations of clusters alone.Comment: 10 pages plus 5 figures; approved for publication in PAS