2,149 research outputs found

    BIMA and Keck Imaging of the Radio Ring PKS 1830-211

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    We discuss BIMA (Berkeley Illinois Maryland Association) data and present new high quality optical and near-IR Keck images of the bright radio ring PKS 1830-211. Applying a powerful new deconvolution algorithm we have been able to identify both images of the radio source. In addition we recover an extended source in the optical, consistent with the expected location of the lensing galaxy. The source counterparts are very red, I-K=7, suggesting strong Galactic absorption with additional absorption by the lensing galaxy at z=0.885, and consistent with the detection of high redshift molecules in the lens.Comment: To be published in the ASP Conference Proceedings, 'Highly Redshifted Radio Lines', Greenbank, W

    The redshift of the gravitationally lensed radio source PKS1830-211

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    We report on the spectroscopic identification and the long awaited redshift measurement of the heavily obscured, gravitationally lensed radio source PKS 1830-211, which was first observed as a radio Einstein ring. The NE component of the doubly imaged core is identified, in our infrared spectrum covering the wavelength range 1.5-2.5 microns, as an impressively reddened quasar at z=2.507. Our redshift measurement, together with the recently measured time delay (Lovell et al.), means that we are a step closer to determining the Hubble constant from this lens. Converting the time delay into the Hubble constant by using existing models leads to high values for the Hubble constant. Since the lensing galaxy lies very close to the center of the lensed ring, improving the error bars on the Hubble constant will require not only a more precise time delay measurement, but also very precise astrometry of the whole system.Comment: 11 pages, 2 figures, Accepted ApJ

    Ceramic Utilization of Northern Kansas Pleistocene Loesses and Fossil Soils

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    Late Pleistocene loesses, classed as Loveland, Peoria, and Bignell silt members of the Sanborn formation, and their contained fossil soils (Loveland and Brady) constitute the most widespread ceramic raw material in Kansas. The silt deposits were made by the action of winds on stream-borne sediments during intervals of northern and mountain glaciation. The silts were modified by weathering processes that produced deep soils on former upper surfaces, now buried by younger deposits. These silts and soils were sampled at 46 localities extending from the Missouri River on the east to the Colorado State line. Ceramic tests on 318 samples and chemical analyses of 52 samples are reported. Spectrographic analyses supplement the ceramic and chemical data. The data show a high degree of uniformity from east to west but the greater effect of weathering in the eastern part of the State has increased the clay content and plastic properties. The Loveland is especially suitable for manufacture of brick, tile, and light-weight ceramic aggregates. The Peoria silt (exclusive of the Brady soil) is suitable for manufacture of dense "ceramic slag." At many localities the entire thickness of the Sanborn formation, including the fossil soils, may be utilized as raw material for brick, tile, and both light and heavy ceramic aggregates

    CLASH-VLT: Testing the Nature of Gravity with Galaxy Cluster Mass Profiles

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    We use high-precision kinematic and lensing measurements of the total mass profile of the dynamically relaxed galaxy cluster MACS J1206.2-0847 at z=0.44z=0.44 to estimate the value of the ratio η=Ψ/Φ\eta=\Psi/\Phi between the two scalar potentials in the linear perturbed Friedmann-Lemaitre-Robertson-Walker metric.[...] Complementary kinematic and lensing mass profiles were derived from exhaustive analyses using the data from the Cluster Lensing And Supernova survey with Hubble (CLASH) and the spectroscopic follow-up with the Very Large Telescope (CLASH-VLT). Whereas the kinematic mass profile tracks only the time-time part of the perturbed metric (i.e. only Φ\Phi), the lensing mass profile reflects the contribution of both time-time and space-space components (i.e. the sum Φ+Ψ\Phi+\Psi). We thus express η\eta as a function of the mass profiles and perform our analysis over the radial range 0.5 Mpc≤r≤r200=1.96 Mpc0.5\,Mpc\le r\le r_{200}=1.96\,Mpc. Using a spherical Navarro-Frenk-White mass profile, which well fits the data, we obtain \eta(r_{200})=1.01\,_{-0.28}^{+0.31} at the 68\% C.L. We discuss the effect of assuming different functional forms for mass profiles and of the orbit anisotropy in the kinematic reconstruction. Interpreting this result within the well-studied f(R)f(R) modified gravity model, the constraint on η\eta translates into an upper bound to the interaction length (inverse of the scalaron mass) smaller than 2 Mpc. This tight constraint on the f(R)f(R) interaction range is however substantially relaxed when systematic uncertainties in the analysis are considered. Our analysis highlights the potential of this method to detect deviations from general relativity, while calling for the need of further high-quality data on the total mass distribution of clusters and improved control on systematic effects.Comment: 18 pages, 3 figures, submitted to JCA

    The effects of changes in thyroid function on testis 32P uptake and the response to gonadotropin in the chick

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    Propylthiouracil (PTU)-induced hypothroidism has been shown to produce a significant increase in the uptake of radiophosphorus (32P) by the testes of young chicks. Continued investigation of this effect demonstrated that thyroidectomy of young birds resulted in elevations in testis 32P uptake comparable to those observed following the administration of PTU. It would thus appear that the increased levels of 32P in the testes of PTU-treated chicks resulted from the hypothyroid condition itself rather than from some other pharmacological action of PTU. A time course study indicated that there were no differences in the turnover rates of labeled testicular phosphorus in hypo-, hyper-, and euthyroid birds which might account for the above observations.Sensitivity of the chick testis to pregnant mare's serum gonadotropin (PMSG) was unaffected by changes in thyroid activity, and the combined effects of PMSG and hypothyroidism on the testis were seemingly additive. Alternative possibilities to explain the apparent indirect effect of subnormal thyroid activity on the testis were therefore discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21803/1/0000203.pd

    Secondary gamma-ray production in a coded aperture mask

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    The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line

    Synthetic approaches to coronafacic acid, coronamic acid, and coronatine

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    The phytotoxin coronatine (COR) is a functional mimic of the active plant hormone (+)-7-iso-jasmonoyl-l-isoleucine (JA-IIe), which regulates stress responses. Structurally, COR is composed of a core unit, coronafacic acid (CFA), which is connected to coronamic acid (CMA), via an amide linkage. COR has been found to induce a range of biological activity in plants and based on its biological profile, COR, as well as CFA, and CMA are attractive starting points for agrochemical discovery, resulting in numerous total synthesis efforts. This review will discuss the synthetic approaches towards CFA, CMA and, ultimately COR, to date

    CLASH-VLT: Environment-driven evolution of galaxies in the z=0.209 cluster Abell 209

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    The analysis of galaxy properties and the relations among them and the environment, can be used to investigate the physical processes driving galaxy evolution. We study the cluster A209 by using the CLASH-VLT spectroscopic data combined with Subaru photometry, yielding to 1916 cluster members down to a stellar mass of 10^{8.6} Msun. We determine: i) the stellar mass function of star-forming and passive galaxies; ii) the intra-cluster light and its properties; iii) the orbits of low- and high-mass passive galaxies; and iv) the mass-size relation of ETGs. The stellar mass function of the star-forming galaxies does not depend on the environment, while the slope found for passive galaxies becomes flatter in the densest region. The color distribution of the intra-cluster light is consistent with the color of passive members. The analysis of the dynamical orbits shows that low-mass passive galaxies have tangential orbits, avoiding small pericenters around the BCG. The mass-size relation of low-mass passive ETGs is flatter than that of high mass galaxies, and its slope is consistent with that of field star-forming galaxies. Low-mass galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio between stellar and number density profiles shows a mass segregation in the center. The comparative analysis of the stellar and total density profiles indicates that this effect is due to dynamical friction. Our results are consistent with a scenario in which the "environmental quenching" of low-mass galaxies is due to mechanisms such as harassment out to R200, starvation and ram-pressure stripping at smaller radii, as supported by the analysis of the mass function, of the dynamical orbits and of the mass-size relation of passive early-types in different regions. Our analyses support the idea that the intra-cluster light is formed through the tidal disruption of subgiant galaxies.Comment: 17 pages, 20 figures, A&A in pres

    Operating characteristics of a prototype high energy gamma-ray telescope

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    The field of gamma-ray astronomy in the energy range from ten to several hundred MeV is severely limited by the angular resolution that can be achieved by present instruments. The identification of some of the point sources found by the COS-B mission and the resolution of detailed structure existing in those sources may depend on the development of a new class of instrument. The coded aperture mask telescope, used successfully at X-ray energies hold the promise of being such an instrument. A prototype coded aperture telescope was operated in a tagged photon beam ranging in energy from 23 to 123 MeV. The purpose of the experiment was to demonstrate the feasibility of operating a coded aperture mask telescope in this energy region. Some preliminary results and conclusions drawn from some of the data resulting from this experiment are presented

    WCDRR and the CEOS activities on disaters

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    Agencies from CEOS (Committee on Earth Observation Satellites) have traditionally focused their efforts on the response phase. Rapid urbanization and increased severity of weather events has led to growing economic and human losses from disasters, requiring international organisations to act now in all disaster risk management (DRM) phases, especially through improved disaster risk reduction policies and programmes. As part of this effort, CEOS agencies have initiated a series of actions aimed at fostering the use of Earth observation (EO) data to support disaster risk reduction and at raising the awareness of policy and decision-makers and major stakeholders of the benefits of using satellite EO in all phases of DRM. CEOS is developing a long-term vision for sustainable application of satellite EO to all phases of DRM. CEOS is collaborating with regional representatives of the DRM user community, on a multi-hazard project involving three thematic pilots (floods, seismic hazards and volcanoes) and a Recovery Observatory that supports resilient recovery from one major disaster. These pilot activities are meant as trail blazers that demonstrate the potential offered by satellite EO for comprehensive DRM. In the framework of the 2015 3rd World Conference on Disaster Risk Reduction (WCDRR), the CEOS space agencies intend to partner with major stakeholders, including UN organizations, the Group on Earth Observations (GEO), international relief agencies, leading development banks, and leading regional DRM organisations, to define and implement a 15-year plan of actions (2015- 2030) that responds to high-level Post-2015 Framework for Disaster Risk Reduction priorities. This plan of action will take into account lessons learned from the CEOS pilot activities
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