187 research outputs found

    A new approach to the reduction of "Carte du Ciel" plates

    Get PDF
    A new procedure for the reduction of "Carte du Ciel" plates is presented. A typical "Carte du Ciel" plate corresponding to the Bordeaux zone has been taken as an example. It shows triple exposures for each object and the modelling of the data has been performed by means of a non-linear least squares fitting of the sum of three bivariate Gaussian distributions. A number of solutions for the problems present in this kind of plates (optical aberrations, adjacency photographic effects, presence of grid lines, emulsion saturation) have been investigated. An internal accuracy of 0.1'' in x and y was obtained for the position of each of the individual exposures. The external reduction to a catalogue led to results with an accuracy of 0.16'' in x and 0.13'' in y for the mean position of the three exposures. A photometric calibration has also been performed and magnitudes were determined with an accuracy of 0.09 mags.Comment: 10 pages, 12 enclosed post-script figures, uses l-aa.sty (included). Accepted for publication in Astronomy and Astrophysics Supp. Serie

    Scaling Relations for Collision-less Dark Matter Turbulence

    Full text link
    Many scaling relations are observed for self-gravitating systems in the universe. We explore the consistent understanding of them from a simple principle based on the proposal that the collision-less dark matter fluid terns into a turbulent state, i.e. dark turbulence, after crossing the caustic surface in the non-linear stage. The dark turbulence will not eddy dominant reflecting the collision-less property. After deriving Kolmogorov scaling laws from Navier-Stokes equation by the method similar to the one for Smoluchowski coagulation equation, we apply this to several observations such as the scale-dependent velocity dispersion, mass-luminosity ratio, magnetic fields, and mass-angular momentum relation, power spectrum of density fluctuations. They all point the concordant value for the constant energy flow per mass: 0.3cm2/sec30.3 cm^2/sec^3, which may be understood as the speed of the hierarchical coalescence process in the cosmic structure formation.Comment: 26 pages, 6 figure

    Binding Energy and the Fundamental Plane of Globular Clusters

    Full text link
    A physical description of the fundamental plane of Galactic globular clusters is developed which explains all empirical trends and correlations in a large number of cluster observables and provides a small but complete set of truly independent constraints on theories of cluster formation and evolution in the Milky Way. Within the theoretical framework of single-mass, isotropic King models, it is shown that (1) 39 regular (non--core-collapsed) globulars with measured core velocity dispersions share a common V-band mass-to-light ratio of 1.45 +/- 0.10, and (2) a complete sample of 109 regular globulars reveals a very strong correlation between cluster binding energy and total luminosity, regulated by Galactocentric position: E_b \propto (L^{2.05} r_{\rm gc}^{-0.4}). The observational scatter about either of these two constraints can be attributed fully to random measurement errors, making them the defining equations of a fundamental plane for globular clusters. A third, weaker correlation, between total luminosity and the King-model concentration parameter, c, is then related to the (non-random) distribution of globulars on the plane. The equations of the FP are used to derive expressions for any cluster observable in terms of only L, r_{\rm gc}, and c. Results are obtained for generic King models and applied specifically to the globular cluster system of the Milky Way.Comment: 60 pages with 19 figures, submitted to Ap

    Some Aspects of Rotational and Magnetic Energies for a Hierarchy of Celestial Objects

    Full text link
    Celestial objects, from earth like planets to clusters of galaxies, possess angular momentum and magnetic fields. Here we compare the rotational and magnetic energies of a whole range of these celestial objects together with their gravitational self energies and find a number of interesting relationships. The celestial objects, due to their magnetic fields, also posses magnetic moments. The ratio of magnetic moments of these objects with the nuclear magnetic moments also exhibits interesting trends. We also compare their gyromagnetic ratio which appears to fall in a very narrow range for the entire hierarchy of objects. Here we try to understand the physical aspects implied by these observations and the origin of these properties in such a wide range of celestial objects, spanning some twenty orders in mass, magnetic field and other parameters.Comment: 12 pages, 37 equation

    A GLIMPSE into the Nature of Galactic Mid-IR Excesses

    Full text link
    We investigate the nature of the mid-IR excess for 31 intermediate-mass stars that exhibit an 8 micron excess in either the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire or the Mid-Course Space Experiment using high resolution optical spectra to identify stars surrounded by warm circumstellar dust. From these data we determine projected stellar rotational velocities and estimate stellar effective temperatures for the sample. We estimate stellar ages from these temperatures, parallactic distances, and evolutionary models. Using MIPS [24] measurements and stellar parameters we determine the nature of the infrared excess for 19 GLIMPSE stars. We find that 15 stars exhibit Halpha emission and four exhibit Halpha absorption. Assuming that the mid-IR excesses arise in circumstellar disks, we use the Halpha fluxes to model and estimate the relative contributions of dust and free-free emission. Six stars exhibit Halpha fluxes that imply free-free emission can plausibly explain the infrared excess at [24]. These stars are candidate classical Be stars. Nine stars exhibit Halpha emission, but their Halpha fluxes are insufficient to explain the infrared excesses at [24], suggesting the presence of a circumstellar dust component. After the removal of the free-free component in these sources, we determine probable disk dust temperatures of Tdisk~300-800 K and fractional infrared luminosities of L(IR)/L(*)~10^-3. These nine stars may be pre-main-sequence stars with transitional disks undergoing disk clearing. Three of the four sources showing Halpha absorption exhibit circumstellar disk temperatures ~300-400 K, L(IR)/L(*)~10^-3, IR colors K-[24]< 3.3, and are warm debris disk candidates. One of the four Halpha absorption sources has K-[24]> 3.3 implying an optically thick outer disk and is a transition disk candidate.Comment: 17 figures. Accepted for publication in Ap

    The Worst Distortions of Astrometric Instruments and Orthonormal Models for Rectangular Fields of View

    Full text link
    The non-orthogonality of algebraic polynomials of field coordinates traditionally used to model field-dependent corrections to astrometric measurements, gives rise to subtle adverse effects. In particular, certain field dependent perturbations in the observational data propagate into the adjusted coefficients with considerable magnification. We explain how the worst perturbation, resulting in the largest solution error, can be computed for a given non-orthogonal distortion model. An algebraic distortion model of full rank can be converted into a fully orthonormal model based on the Zernike polynomials for a circular field of view, or a basis of functions constructed from the original model by a variant of the Gram-Schmidt orthogonalization process for a rectangular field of view. The relative significance of orthonormal distortion terms is assessed simply by the numerical values of the corresponding coefficients. Orthonormal distortion models are easily extendable when the distribution of residuals indicate the presence of higher order terms.Comment: 1 figure; submitted in PAS

    Astrometry and geodesy with radio interferometry: experiments, models, results

    Full text link
    Summarizes current status of radio interferometry at radio frequencies between Earth-based receivers, for astrometric and geodetic applications. Emphasizes theoretical models of VLBI observables that are required to extract results at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the achievements of VLBI during the past two decades in reference frames, Earth orientation, atmospheric effects on microwave propagation, and relativity.Comment: 83 pages, 19 Postscript figures. To be published in Rev. Mod. Phys., Vol. 70, Oct. 199

    Cosmology, Oscillating Physics and Oscilllating Biology

    Get PDF
    According to recent reports there is an excess correlation and an apparent regularity in the galaxy one-dimensional polar distribution with a characteristic scale of 128 h−1h^{-1} Mpc. This aparent spatial periodicity can be naturally explained by a time oscillation of the gravitational constant GG. On the other hand, periodic growth features of bivalve and coral fossiles appear to show a periodic component in the time dependence of the number of days per year. In this letter we show that a time oscillating gravitational constant with similar period and amplitude can explain such a feature.Comment: 9 pages. latex using revtex. This revised version is supposed to be free of e-mail nois

    Relict periglacial soils on Quaternary terraces in the central Ebro Basin (NE Spain)

    Get PDF
    Pedofeatures associated with ancient cold climatic conditions have been recognized in soils on terraces in the Monegros area (central Ebro Basin, Spain), at a latitude of 41°49â€ČN and an altitude of 300 m a.s.l. Eleven soil profiles were described on fluvial deposits corresponding to the most extensive terrace (T5) of the Alcanadre River, Middle Pleistocene in age (MIS8–MIS7). Each soil horizon was sampled for physical, chemical, mineralogical and micromorphological analyses. Macromorphological features related to pedocryogenic processes were described: involutions, jacked stones, shattered stones, detached and vertically oriented carbonatic pendents, fragmented carbonatic crusts, laminar microstructures, succitic fabric, silt cappings on rock fragments and aggregates, and irregular, broken, discontinuous and deformed gravel and sandy pockets. Accumulations of Fe–Mn oxides, dissolution features on the surface of carbonatic stones, and calcitic accumulations were identified related to vadose–phreatic conditions. The observed periglacial features developed under cold environmental conditions in exceptional geomorphic and hydrological conditions. This soil information may have potential implications in studies of paleoclimate in the Ebro Valley as well as in other Mediterranean areas

    Rotation Curve of Galaxies by the Force Induced by Mass of Moving Particles

    Full text link
    We suggest that there is a novel force which is generated by the mass of relatively moving particles. The new force which we named Mirinae Force is a counterpart of the magnetic force operating between electrically charged moving particles. Instead of using the conventional dark matter, we applied the mirinae force to a particular model system of the spiral galaxy in which most of the galaxy's mass is located within the central region where some portion of the inner mass is in revolving motion at a relativistic speed. The calculation yielded three important results that illustrate the existence of mirinae force and validate the proposed model: First, the mirinae force in this model explains why most of the matters in the galactic disk are in the circular motion which is similar to cycloid. Second, the mirinae force well explains not only the flat rotation curve but also the varied slope of the rotation curve observed in the spiral galaxies. Third, at the flat velocity of 220 Km/s, the inner mass of the Milky Way calculated by using the proposed model is 6.0\times10^11 M\odot, which is very close to 5.5\times10^11 M\odot (r <50 Kpc, including Leo I) estimated by using the latest kinematic information. This means that the mirinae force well takes the place of the dark matter of the Milky Way
    • 

    corecore