6,109 research outputs found

    The Asymmetric Thick Disk: A Star Count and Kinematic Analysis. II The Kinematics

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    We report a kinematic signature associated with the observed asymmetry in the distribution of thick disk/inner halo stars interior to the Solar circle described in Paper I. In that paper we found a statistically significant excess (20% to 25 %) of stars in quadrant I (l ~ 20 deg to 55 deg) both above and below the plane (b ~ +/- 25 deg to +/- 45 deg) compared to the complementary region in quadrant IV. We have measured Doppler velocities for 741 stars, selected according to the same magnitude and color criteria, in the direction of the asymmetry and in the corresponding fields in quadrant IV. We have also determined spectral types and metallicities measured from the same spectra. We not only find an asymmetric distribution in the V_LSR velocities for the stars in the two regions, but the angular rate of rotation, w, for the stars in quadrant I reveals a slower effective rotation rate compared to the corresponding quadrant IV stars. We use our [Fe/H] measurements to separate the stars into the three primary population groups, halo, thick disk, and disk, and conclude that it is primarily the thick disk stars that show the slower rotation in quadrant I. A solution for the radial, tangential and vertical components of the V_LSR velocities, reveals a significant lag of ~ 80 to 90 km/s in the direction of Galactic rotation for the thick disk stars in quadrant I, while in quadrant IV, the same population has only a ~ 20 km/s lag. The results reported here support a rotational lag among the thick disk stars due to a gravitational interaction with the bar as the most likely explanation for the asymmetry in both the star counts and the kinematics. The affected thick disk stars, however, may be associated with the recently discovered Canis Major debris stream or a similar merger event (abridged).Comment: Accepted for publication in the Astronomical Journa

    An economic evaluation of tick line deregulation in Queensland

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    Rhipicephalus microplus, the cattle tick, is widely distributed across many tropical and subtropical regions of the world and has been identified as the most economically important species of tick across a number of countries. Quarantine boundaries currently limit the spread of the cattle tick into northern New South Wales, parts of South East Queensland, the central parts of the Northern Territory and northern parts of Western Australia. The Queensland tick line (or quarantine boundary) largely follows the 500mm rainfall isohyet until it reaches southern Queensland. As the cattle tick is unlikely to become endemic to regions receiving median rainfall less than 500mm per annum, the region most likely to be effected by a deregulation of the tick line is located in the south east corner of the State “inside” the 500mm isohyet but “outside” of the tick line. There are a number of strategies available to beef producers running susceptible cattle within the region impacted by a deregulation of the tick line. For example, they could: o choose to apply acaricides into the foreseeable future, o choose to breed tick resistance into their livestock and apply acaricides during the conversion period, o replace their susceptible breeding herds with tick resistant stock from within the tick endemic region, or o continue with susceptible livestock and implement sufficient quarantine and pest management strategies to reduce the risk of tick infestation to a negligible level The economic evaluation of these strategies indicates that the total costs of deregulation depend upon the type of response made by industry and the level of that response.Resource /Energy Economics and Policy,

    A solução de controvérsias na OMC

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    Divulgação dos SUMÁRIOS das obras recentemente incorporadas ao acervo da Biblioteca Ministro Oscar Saraiva do STJ. Em respeito à lei de Direitos Autorais, não disponibilizamos a obra na íntegra. STJ00076934 339.5 A485

    Iowa Lottery Performance Report, FY2007

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    Agency Performance Repor

    ALMA Observations of the Submillimeter Dense Molecular Gas Tracers in the Luminous Type-1 Active Nucleus of NGC 7469

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    We present ALMA Cycle 1 observations of the central kpc region of the luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.5"" ×\times 0.4"" = 165 pc ×\times 132 pc) at submillimeter wavelengths. Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO+^+(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 ÎŒ\mum continuum. The region consists of the central ∌\sim 1"" component and the surrounding starburst ring with a radius of ∌\sim 1.5""-2.5"". Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated towards the central ∌\sim 1"", suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anti-correlated with the optical one, indicating the existence of dust obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO+^+(4-3) and HCN(4-3)/CS(7-6) are higher at the AGN position than at the starburst ring, which is consistent to our previous findings (submm-HCN enhancement). However, the HCN(4-3)/HCO+^+(4-3) ratio at the AGN position of NGC 7469 (1.11±\pm0.06) is almost half of the corresponding value of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.0±\pm0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (∌\sim 1.5). Based on these results, we speculate that some other heating mechanisms than X-ray (e.g., mechanical heating due to AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.Comment: Fixed typos in the title. 15 pages, 8 figures, 4 tables: accepted for publication in ApJ. Comments welcom

    The Submillimeter Array Polarimeter

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    We describe the Submillimeter Array (SMA) Polarimeter, a polarization converter and feed multiplexer installed on the SMA. The polarimeter uses narrow-band quarter-wave plates to generate circular polarization sensitivity from the linearly-polarized SMA feeds. The wave plates are mounted in rotation stages under computer control so that the polarization handedness of each antenna is rapidly selectable. Positioning of the wave plates is found to be highly repeatable, better than 0.2 degrees. Although only a single polarization is detected at any time, all four cross correlations of left- and right-circular polarization are efficiently sampled on each baseline through coordinated switching of the antenna polarizations in Walsh function patterns. The initial set of anti-reflection coated quartz and sapphire wave plates allows polarimetry near 345 GHz; these plates have been have been used in observations between 325 and 350 GHz. The frequency-dependent cross-polarization of each antenna, largely due to the variation with frequency of the retardation phase of the single-element wave plates, can be measured precisely through observations of bright point sources. Such measurements indicate that the cross-polarization of each antenna is a few percent or smaller and stable, consistent with the expected frequency dependence and very small alignment errors. The polarimeter is now available for general use as a facility instrument of the SMA.Comment: To appear in Proc. SPIE 7020, 'Millimeter and Submillimeter Detectors and Instrumentation'. Uses spie.cl
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