10,450 research outputs found

    Filaments in Galactic Winds Driven by Young Stellar Clusters

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    The starburst galaxy M82 shows a system of Hα\alpha-emitting filaments which extend to each side of the galactic disk. We model these filaments as the result of the interaction between the winds from a distribution of Super Stellar Clusters (SSCs). We first derive the condition necessary for producing a radiative interaction between the cluster winds (a condition which is met by the SSC distribution of M82). We then compute 3D simulations for SSC wind distributions which satisfy the condition for a radiative interaction, and also for distributions which do not satisfy this condition. We find that the highly radiative models, that result from the interaction of high metallicity cluster winds, produce a structure of Hα\alpha emitting filaments, which qualitatively agrees with the observations of the M82, while the non-radiative SSC wind interaction models do not produce filamentary structures. Therefore, our criterion for radiative interactions (which depends on the mass loss rate and the terminal velocity of the SSC winds, and the mean separation between SSCs) can be used to predict whether or not an observed galaxy should have associated Hα\alpha emitting filaments.Comment: 10 pages, 6 Figures. ApJ Accepted, August 7, 200

    Ultracold heteronuclear molecules and ferroelectric superfluids

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    We analyze the possibility of a ferroelectric transition in heteronuclear molecules consisting of Bose-Bose, Bose-Fermi or Fermi-Fermi atom pairs. This transition is characterized by the appearance of a spontaneous electric polarization below a critical temperature. We discuss the existence of a ferroelectric Fermi liquid phase for Fermi molecules and the existence of a ferroelectric superfluid phase for Bose molecules characterized by the coexistence of ferroelectric and superfluid orders. Lastly, we propose an experiment to detect ferroelectric correlations through the observation of coherent dipole radiation pulses during time of flight.Comment: 4 pages and 3 figure

    Life history of white stumpnose Rhabdosargus globiceps (Pisces: Sparidae) off South Africa

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    Fishery-dependent and fishery-independent distribution analyses together reveal four discrete areas of white stumpnose Rhabdosargus globiceps abundance between Port Nolloth and the Kei River off the Cape Province of South Africa: the Western Cape (Saldanha Bay), the South-Western Cape, the Southern Cape and the South-Eastern Cape. On the basis of migratory patterns determined from tagging and catch data, and on differences in growth rate and size-at-maturity, it is concluded that these areas of abundance represent four separate stocks. Each stock apparently disperses offshore in winter (to c. 130 m depth) and concentrates inshore

    DNA plasmidial de isolados patogĂȘnicos de Xanthomonas campestris pv. viticola.

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    Poucos sĂŁo os estudos a respeito da presença de plasmĂ­deos neste patĂłgeno. Nos animais, bactĂ©rias patogĂȘnicas sĂŁo conhecidas por albergar plasmĂ­deos com diferentes funçÔes entre elas a resistĂȘncia, metabolismo de produtos tĂłxicos e transferĂȘncia de material genĂ©tico (Sherley et al., 2004). Nosso estudo teve por objetivo caracterizar o conteĂșdo de plasmĂ­deos de isolados de X. campestris pv viticola isoladas de casos clĂ­nicos

    Young Super Star Clusters in the Starburst of M82: The Catalogue

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    Recent results from Hubble Space Telescope (HST) have resolved starbursts as collections of compact young stellar clusters. Here we present a photometric catalogue of the young stellar clusters in the nuclear starburst of M82, observed with the HST WFPC2 in Halpha (F656N) and in four optical broad-band filters. We identify 197 young super stellar clusters. The compactness and high density of the sources led us to develop specific techniques to measure their sizes. Strong extinction lanes divide the starburst into five different zones and we provide a catalogue of young super star clusters for each of these. In the catalogue we include relative coordinates, radii, fluxes, luminosities, masses, equivalent widths, extinctions, and other parameters. Extinction values have been derived from the broad-band images. The radii range between 3 and 9 pc, with a mean value of 5.7 +/- 1.4pc, and a stellar mass between 10e4 and 10e6 Mo. The inferred masses and mean separation, comparable to the size of super star clusters, together with their high volume density, provides strong evidence for the key ingredients postulated by Tenorio et al. (2003) as required for the development of a supergalactic wind.Comment: 45 pages, 5 figures, 12 tables. Accepted for publication in ApJ. Added Erratu

    Herman's Theory Revisited

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    We prove that a C2+αC^{2+\alpha}-smooth orientation-preserving circle diffeomorphism with rotation number in Diophantine class DÎŽD_\delta, 0<ÎŽ<α≀10<\delta<\alpha\le1, is C1+α−ΎC^{1+\alpha-\delta}-smoothly conjugate to a rigid rotation. We also derive the most precise version of Denjoy's inequality for such diffeomorphisms.Comment: 10 page
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