1,991 research outputs found

    The Globular Cluster System of the Spiral Galaxy NGC7814

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    We present the results of a wide-field photometric study of the globular cluster (GC) system of the edge-on Sab spiral NGC7814. This is the first spiral to be fully analyzed from our survey of the GC systems of a large sample of galaxies beyond the Local Group. NGC7814 is of particular interest because a previous study estimated that it has 500-1000 GCs, giving it the largest specific frequency (S_N) known for a spiral. Understanding this galaxy's GC system is important in terms of our understanding of the GC populations of spirals in general and has implications for the formation of massive galaxies. We observed the galaxy in BVR filters with the WIYN 3.5-m telescope, and used image classification and three-color photometry to select GC candidates. We also analyzed archival HST WFPC2 images of NGC7814, both to help quantify the contamination level of the WIYN GC candidate list and to detect GCs in the inner part of the galaxy halo. Combining HST data with high-quality ground-based images allows us to trace the entire radial extent of this galaxy's GC system and determine the total number of GCs directly through observation. We find that rather than being an especially high-S_N spiral, NGC7814 has <200 GCs and S_N ~ 1, making it comparable to the two most well-studied spirals, the Milky Way and M31. We explore the implications of these results for models of the formation of galaxies and their GC systems. The initial results from our survey suggest that the GC systems of typical ellipticals can be accounted for by the merger of two or more spirals, but that for highly-luminous ellipticals, additional physical processes may be needed.Comment: 28 pages, incl. 4 figures; accepted for publication in The Astronomical Journal, November 2003 issu

    Determining the galactic mass distribution using tidal streams from globular clusters

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    We discuss how to use tidal streams from globular clusters to measure the mass distribution of the Milky Way. Recent proper motion determinations for globular clusters from plate measurements and Hipparcos astrometry provide several good candidates for Galactic mass determinations in the intermediate halo, far above the Galactic disk, including Pal 5, NGC 4147, NGC 5024 (M53) and NGC 5466; the remaining Hipparcos clusters provide candidates for measurements several kpc above and below the disk. These clusters will help determine the profile and shape of the inner halo. To aid this effort, we present two methods of mass determination: one, a generalization of rotation-curve mass measurements, which gives the mass and potential from complete position-velocity observations for stream stars; and another using a simple chi^2 estimator, which can be used when only projected positions and radial velocities are known for stream stars. We illustrate the use of the latter method using simulated tidal streams from Pal 5 and find that fairly accurate mass determinations are possible even for relatively poor data sets. Follow-up observations of clusters with proper motion determinations may reveal tidal streams; obtaining radial velocity measurements would enable accurate measurements of the mass distribution in the inner Galaxy.Comment: 21 pages, 6 figures, published in A

    Generalized synchronization: a modified system approach

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    The universal mechanism resulting in the generalized synchronization regime arising in the chaotic oscillators with the dissipative coupling has been described. The reasons of the generalized synchronization occurrence may be clarified by means of a modified system approach. The main results are illustrated by unidirectionally coupled Rossler systems, Rossler and Lorenz systems and logistic maps.Comment: 4 pages, 2 figure

    Modeling the dynamical evolution of the M87 globular cluster system

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    We study the dynamical evolution of the M87 globular cluster system (GCS) with a number of numerical simulations. We explore a range of different initial conditions for the GCS mass function (GCMF), for the GCS spatial distribution and for the GCS velocity distribution. We confirm that an initial power-law GCMF like that observed in young cluster systems can be readily transformed through dynamical processes into a bell-shaped GCMF. However,only models with initial velocity distributions characterized by a strong radial anisotropy increasing with the galactocentric distance are able to reproduce the observed constancy of the GCMF at all radii.We show that such strongly radial orbital distributions are inconsistent with the observed kinematics of the M87 GCS. The evolution of models with a bell-shaped GCMF with a turnover similar to that currently observed in old GCS is also investigated. We show that models with this initial GCMF can satisfy all the observational constraints currently available on the GCS spatial distribution,the GCS velocity distribution and on the GCMF properties.In particular these models successfully reproduce both the lack of a radial gradient of the GCS mean mass recently found in an analysis of HST images of M87 at multiple locations, and the observed kinematics of the M87 GCS.Our simulations also show that evolutionary processes significantly affect the initial GCS properties by leading to the disruption of many clusters and changing the masses of those which survive.The preferential disruption of inner clusters flattens the initial GCS number density profile and it can explain the rising specific frequency with radius; we show that the inner flattening observed in the M87 GCS spatial distribution can be the result of the effects of dynamical evolution on an initially steep density profile. (abridged)Comment: 15 pages,14 figures;accepted for publication in The Astrophysical Journa

    Formation and evolution of clumpy tidal tails around globular clusters

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    We present some results of numerical simulations of a globular cluster orbiting in the central region of a triaxial galaxy on a set of 'loop' orbits. Tails start forming after about a quarter of the globular cluster orbital period and develop, in most cases, along the cluster orbit, showing clumpy substructures as observed, for example, in Palomar 5. If completely detectable, clumps can contain about 7,000 solar masses each, i.e. about 10% of the cluster mass at that epoch. The morphology of tails and clumps and the kinematical properties of stars in the tails are studied and compared with available observational data. Our finding is that the stellar velocity dispersion tends to level off at large radii, in agreement to that found for M15 and Omega Centauri.Comment: LaTeX 2e, uses AASTeX v5.x, 40 pages with 18 figures. Submitted to The Astronomical Journa

    Performance Analysis of Red Chilli in a Hybrid Collector with Solar Dryer

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    This article performed various analysis on Red chilli by hybrid collector with solar dryer (HCSD). This study was carried out forced convection solar dryer which performed better in all aspects such as drying time, moisture removal rate, electrical efficiency, electrical thermal efficiency, thermal efficiency and overall thermal efficiency. In general, solar radiation was provided a sources of generating energy to drive a solar dryer. Hybrid collector has been provided the electrical and thermal energy to run a solar dryer. The solar dryer was tested by drying 12 kg of red chilli in the drying air temperature in the range of 32 0C – 56 0C. The initial moisture content of the red chilli was 71.5 % (weight basis) and was reduced to the final moisture content of 16.2 % (weight basis) in 6 consistent days with clear sunny days. The HCSD was operated between 9 hrs to 16 hrs. Finally, comparative study was also handled for better understanding in HCSD, in which solar dryer drying made better outcome than open sun drying

    AN ANALYSIS OF INTERNATIONAL PRICE AND EXCHANGE RATE ELASTICITY FOR US SOYBEANS: THE CASE OF JAPAN

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    Stepwise model selection criteria were tested against the restrictive forms to determine the appropriate model and to confirm the law of one price for the US soybeans. Analysis shows less than one international price transmission and exchange rate elasticities in the long run indicate an incomplete exchange rate pass through.International Relations/Trade,

    Measuring the Impacts of US Export Promotion Program for Wheat in Selected Importing Regions

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    We examine the impacts of major factors affecting the export demand of wheat with a special focus on the impacts of export promotion programs on US wheat. Study results show negative impacts of own-price and real exchange rate on export demand of wheat, while the real GDP, price of corn, and export promotion expenditure had positive and significant impacts. The per dollar returns to wheat export promotion expenditures were 1.49,1.49, 0.42, and $2.01 for Middle East, Pacific Rim, and Mexico, respectively.International Relations/Trade,

    NON-PRICE PROMOTION IMPACTS ON COTTON AND SOYBEANS EXPORTS UNDER EXCHANGE RATE LINKED SUBSIDIES

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    Issue of exchange rate-linked subsidies for non-price export promotion has recently emerged as an area of interest among marketing researchers because of fluctuating strength of US dollars and position of US agricultural goods in export markets. One solution to mitigate these impacts was to link the federal export promotion subsidies with the changing value of US dollars. In the study, an equilibrium displacement framework was developed to analyze the effectiveness of exchange rate-linked subsidies for non-price promotion by comparatively analyzing its effectiveness on US soybeans and cotton. The study result shows that an increase in promotion expenditure with an increase in the strength of US dollars and vice versa promotes the export of US cotton and soybeans in export markets and increases the efficiency of federal export promotion programs. Even though transportation cost elasticity was one of major focuses of this study, it emerged as an insignificant factor.export promotion, exchange rate linked subsidies, gross gain, and producer welfare, Agricultural and Food Policy, International Relations/Trade,
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