Fragmentation, infall, and outflow around the showcase massive protostar NGC7538 IRS1 at 500 AU resolution

Aims: Revealing the fragmentation, infall, and outflow processes in the immediate environment around massive young stellar objects is crucial for understanding the formation of the most massive stars. Methods: With this goal in mind we present the so far highest spatial-resolution thermal submm line and continuum observations toward the young high-mass protostar NGC7538 IRS1. Using the Plateau de Bure Interferometer in its most extended configuration at 843mum wavelength, we achieved a spatial resolution of 0.2"x0.17", corresponding to ~500AU at a distance of 2.7\,kpc. Results: For the first time, we have observed the fragmentation of the dense inner core of this region with at least three subsources within the inner 3000 AU. The outflow exhibits blue- and red-shifted emission on both sides of the central source indicating that the current orientation has to be close to the line-of-sight, which differs from other recent models. We observe rotational signatures in northeast-southwest direction; however, even on scales of 500 AU, we do not identify any Keplerian rotation signatures. This implies that during the early evolutionary stages any stable Keplerian inner disk has to be very small (<=500 AU). The high-energy line HCN(4-3)v2=1 (E_u/k=1050K) is detected over an extent of approximately 3000 AU. In addition to this, the detection of red-shifted absorption from this line toward the central dust continuum peak position allows us to estimate infall rates of ~1.8x10^(-3)Msun/yr on the smallest spatial scales. Although all that gas will not necessarily be accreted onto the central protostar, nevertheless, such inner core infall rates are among the best proxies of the actual accretion rates one can derive during the early embedded star formation phase. These data are consistent with collapse simulations and the observed high multiplicity of massive stars.Comment: Accepted for Astronomy & Astrophysics, 8 pages, also available at http://www.mpia.de/homes/beuther/papers.htm

TRADE GAINS AND WELFARE COSTS OF INCOME STABILIZATION PROGRAMS FOR HOG PRODUCERS IN QUEBEC

The welfare costs of deficiency payments for an exported commodity may, under certain conditions, outweigh the gains from trade. The potential welfare impacts of stabilization programs in the hog sector in Quebec are estimated, based on a partial equilibrium framework, and elasticity estimates drawn from other sources. The results indicate that the loss in surplus in Quebec as a result of deficiency payments is very modest at approximately $8.5 million or 1.7$14 million.Livestock Production/Industries,

Carbonates in space - The challenge of low temperature data

Carbonates have repeatedly been discussed as possible carriers of stardust emission bands. However, the band assignments proposed so far were mainly based on room temperature powder transmission spectra of the respective minerals. Since very cold calcite grains have been claimed to be present in protostars and in Planetary Nebulae such as NGC 6302, the changes of their dielectric functions at low temperatures are relevant from an astronomical point of view. We have derived the IR optical constants of calcite and dolomite from reflectance spectra - measured at 300, 200, 100 and 10K - and calculated small particle spectra for different grain shapes, with the following results: i) The absorption efficiency factors both of calcite and dolomite are extremely dependent on the particle shapes. This is due to the high peak values of the optical constants of CaCO3 and CaMg[CO3]2. ii) The far infrared properties of calcite and dolomite depend also very significantly on the temperature. Below 200K, a pronounced sharpening and increase in the band strengths of the FIR resonances occurs. iii) In view of the intrinsic strength and sharpening of the 44 mum band of calcite at 200-100K, the absence of this band -- inferred from Infrared Space Observatory data -- in PNe requires dust temperatures below 45K. iv) Calcite grains at such low temperatures can account for the '92' mum band, while our data rule out dolomite as the carrier of the 60-65 mum band. The optical constants here presented are publicly available in the electronic database http://www.astro.uni-jena.de/Laboratory/OCDBComment: 20 pages, 10 figures, accepted by ApJ, corrected typo

Quasiclassical theory for the superconducting proximity effect in Dirac materials

We derive the quasiclassical non-equilibrium Eilenberger and Usadel equations to first order in quantities small compared to the Fermi energy, valid for Dirac edge and surface electrons with spin-momentum locking, as relevant for topological insulators. We discuss in detail several of the key technical points and assumptions of the derivation, and provide a Riccati-parametrization of the equations. Solving first the equilibrium equations for S/N and S/F bilayers and Josephson junctions, we study the superconducting proximity effect in Dirac materials. Similarly to related works, we find that the effect of an exchange field depends strongly on the direction of the field. Only components normal to the transport direction lead to attenuation of the Cooper pair wavefunction inside the F. Fields parallel to the transport direction lead to phase-shifts in the dependence on the superconducting phase difference for both the charge current and density of states in an S/F/S-junction. Moreover, we compute the differential conductance in S/N and S/F bilayers with an applied voltage bias, and determine the dependence on the length of the N and F regions and the exchange field.Comment: 13 pages, 5 figures. Accepted for publication in Phys. Rev.

Meson and Quark Degrees of Freedom and the Radius of the Deuteron

The existing experimental data for the deuteron charge radius are discussed. The data of elastic electron scattering are inconsistent with the value obtained in a recent atomic physics experiment. Theoretical predictions based on a nonrelativistic description of the deuteron with realistic nucleon-nucleon potentials and with a rather complete set of meson-exchange contributions to the charge operator are presented. Corrections arising from the quark-gluon substructure of the nucleon are explored in a nonrelativistic quark model; the quark-gluon corrections, not accounted for by meson exchange, are small. Our prediction for the deuteron charge radius favors the value of a recent atomic physics experiment.Comment: 20 pages, LaTeX, 4 Postscript figures, to appear in Few-Body-System

Sodalite solid solution systems

Diese Arbeit über "Sodalite Solid Solution Systems" befasst sich mit der Synthese und topotaktischen Umwandlungen einer besonderen Form von Festen Lösungen und deren Untersuchung mittels Festkörper Kernspinresonanz (Solid State NMR) und Röntgen-Pulverdiffraktometrie. In Sodalithen {Na6[Al3Si3O12]2*(A,B)2} sind die Gast-spezies (A,B) bei denen es sich sowohl um Salze des Typs NaX als auch um Wasser oder basische Zentren handeln kann statistisch in den Aluminosilikat- Käfigen verteilt. Der nichtlineare Zusammenhang zwischen den Gastionen- Konzentrationen im Synthesegel und Sodalith wurde untersucht für die Systeme (NaX, NaY) mit X,Y = Cl-, Br-, I-, O2H3- und durch ein empirisches Modell beschrieben. Basische Zentren können topotaktisch durch Wasser ersetzt werden, welches den Sodalith bei 400°C verlässt. Durch Bedampfen des trockenen Sodaliths mit elementarem Natrium können (Na4)3+ Farb-Zentren (F-centers) erzeugt werden. Zusammenhänge zwischen NMR Parametern von 1H, 23Na, 27Al, 29Si, 35Cl, 81Br und 127I Kernen und ihrer lokalen Umgebung konnten aufgezeigt und zur Charakterisierung genutzt werden. Schließlich geben temperaturabhängige NMR Untersuchungen Aufschluss über die elektrostatischen und magnetischen Wechselwirkungen zwischen den paramagnetischen Elektronen der F-Zentren

Die p-adischen lokal analytischen Hauptreihen zerfallend reduktiver Gruppen

Die Darstellungstheorie p-adischer Liegruppen zerfällt in einander sehr fremde Bereiche. In erster Linie stehen sich dabei die glatten und die algbraischen Darstellungen gegenüber. Diese können in der jüngst eingeführten Kategorie der lokal analytischen Darstellungen in handhabbarer Weise zusammengeführt werden. Bislang fehlt allerdings ein Überblick über die dort anzutreffenden irreduziblen Darstellungen. In der vorliegenden Arbeit werden nun von endlich dimensionalen Darstellungen parabolisch induzierte Darstellungen untersucht. Die Frage nach der Irreduzibilität lässt sich dabei auf analoge Fragen in der Theorie der Darstellungen von Liealgebren zurückführen. Hier kann man auf die vorhandene reichhaltige Theorie der Vermamoduln zurückgreifen

The role of accretion disks in the formation of massive stars

We present radiation hydrodynamics simulations of the collapse of massive pre-stellar cores. We treat frequency dependent radiative feedback from stellar evolution and accretion luminosity at a numerical resolution down to 1.27 AU. In the 2D approximation of axially symmetric simulations, it is possible for the first time to simulate the whole accretion phase of several 10^5 yr for the forming massive star and to perform a comprehensive scan of the parameter space. Our simulation series show evidently the necessity to incorporate the dust sublimation front to preserve the high shielding property of massive accretion disks. Our disk accretion models show a persistent high anisotropy of the corresponding thermal radiation field, yielding to the growth of the highest-mass stars ever formed in multi-dimensional radiation hydrodynamics simulations. Non-axially symmetric effects are not necessary to sustain accretion. The radiation pressure launches a stable bipolar outflow, which grows in angle with time as presumed from observations. For an initial mass of the pre-stellar host core of 60, 120, 240, and 480 Msol the masses of the final stars formed in our simulations add up to 28.2, 56.5, 92.6, and at least 137.2 Msol respectively.Comment: 4 pages, 2 figures, Computational Star Formation Proceedings IAU Symposium No. 270, 2010, Ed.: J. Alves, B. Elmegreen, J. Girart & V. Trimbl