462 research outputs found

    Nose controls on delta wings at supersonic speeds

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    Expressions are derived for lξ and a2 of nose ailerons and nose elevators on a delta wing, as depicted in Fig. 1, in supersonic flight. Nose and trailing edge controls on delta wings in supersonic flight are compared

    Constraints on a Massive Dirac Neutrino Model

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    We examine constraints on a simple neutrino model in which there are three massless and three massive Dirac neutrinos and in which the left handed neutrinos are linear combinations of doublet and singlet neutrinos. We examine constraints from direct decays into heavy neutrinos, indirect effects on electroweak parameters, and flavor changing processes. We combine these constraints to examine the allowed mass range for the heavy neutrinos of each of the three generations.Comment: latex, 29 pages, 7 figures (not included), MIT-CTP-221

    Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

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    The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

    Performance of the CMS Cathode Strip Chambers with Cosmic Rays

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    The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

    A review of elliptical and disc galaxy structure, and modern scaling laws

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    A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to appear in "Planets, Stars and Stellar Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references incl. many somewhat forgotten, pioneer papers. Original submission to Springer: 07-June-201

    Performance and Operation of the CMS Electromagnetic Calorimeter

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    The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented

    ASKAP HI imaging of the galaxy group IC 1459

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    © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. We present HI imaging of the galaxy group IC 1459 carried out with six antennas of the Australian Square Kilometre Array Pathfinder equipped with phased-array feeds. We detect and resolve HI in 11 galaxies down to a column density of ~1020 cm-2 inside a ~6 deg2 field and with a resolution of ~1 arcmin on the sky and ~8 kms-1 in velocity. We present HI images, velocity fields and integrated spectra of all detections, and highlight the discovery of three HI clouds - two in the proximity of the galaxy IC 5270 and one close to NGC 7418. Each cloud has an HI mass of ~109 M? and accounts for ~15 per cent of the HI associated with its host galaxy. Available images at ultraviolet, optical and infrared wavelengths do not reveal any clear stellar counterpart of any of the clouds, suggesting that they are not gas-rich dwarf neighbours of IC 5270 and NGC 7418. Using Parkes data, we find evidence of additional extended, low-column-density HI emission around IC 5270, indicating that the clouds are the tip of the iceberg of a larger system of gas surrounding this galaxy. This result adds to the body of evidence on the presence of intragroup gas within the IC 1459 group. Altogether, the HI found outside galaxies in this group amounts to several times 109 M?, at least 10 per cent of the HI contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution

    Discovery of HI gas in a young radio galaxy at z = 0.44 using the Australian Square Kilometre Array Pathfinder

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    We report the discovery of a new 21-cm H i absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5–1015.5 MHz band of ASKAP we were able to conduct a blind search for the 21-cm line in a continuous redshift range between z = 0.4 and 1.0, which has, until now, remained largely unexplored. The absorption line is detected at z = 0.44 towards the GHz-peaked spectrum radio source PKS B1740−517 and demonstrates ASKAP's excellent capability for performing a future wide-field survey for H i absorption at these redshifts. Optical spectroscopy and imaging using the Gemini-South telescope indicates that the H i gas is intrinsic to the host galaxy of the radio source. The narrow [O iii] emission lines show clear double-peaked structure, indicating either large-scale outflow or rotation of the ionized gas. Archival data from the XMM–Newton satellite exhibit an absorbed X-ray spectrum that is consistent with a high column density obscuring medium around the active galactic nucleus. The H i absorption profile is complex, with four distinct components ranging in width from 5 to 300 km s−1 and fractional depths from 0.2 to 20 per cent. In addition to systemic H i gas, in a circumnuclear disc or ring structure aligned with the radio jet, we find evidence for a possible broad outflow of neutral gas moving at a radial velocity of v ~ 300 km s−1. We infer that the expanding young radio source (tage ≈ 2500 yr) is cocooned within a dense medium and may be driving circumnuclear neutral gas in an outflow of ~1 M⊙ yr−1
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