50,244 research outputs found

    The Nature of Radio Emission from Distant Galaxies

    Full text link
    I describe an observational program aimed at understanding the radio emission from distant, rapidly evolving galaxy populations. These observations were carried out at 1.4 and 8.5 GHz with the VLA centered on the Hubble Deep Field. Further MERLIN observations of the HDF region at 1.4 GHz provided an angular resolution of 0.2" and when combined with the VLA data produced an image with an unprecedented rms noise of 4 μ\muJy. All radio sources detected in the VLA complete sample are resolved with a median angular size of 1-2". The differential count of the radio sources is marginally sub-Euclidean (γ\gamma = -2.4 ±\pm 0.1) and fluctuation analysis suggests nearly 60 sources per arcmin2^2 are present at the 1 μ\muJy level. A correlation analysis indicates spatial clustering among the 371 radio sources on angular scales of 1- 40 arcmin. Optical identifications are made primarily with bright (I = 22) disk systems composed of irregulars, peculiars, interacting/merging galaxies, and a few isolated field spirals. Available redshifts span the range 0.2 - 3. These clues coupled with the steep spectral index of the 1.4 GHz selected sample are indicative of diffuse synchrotron radiation in distant galactic disks. Thus the evolution in the microjansky radio population is driven principally by star-formation. I have isolated a number of optically faint radio sources (about 25% of the overall sample) which remain unidentified to I = 26-28 in the HDF and flanking optical fields. Several of these objects have extremely red counterparts and constitute a new class of radio sources which are candidate high-z dusty protogalaxies.Comment: dissertation summary to be published in PASP, sucessfully defended on May 19, 1999 at the University of Virginia, committee composed of R. W. O'Connell (UVa), K. I. Kellermann (NRAO), E. B Fomalont (NRAO), T. X. Thuan (UVa), P. Humphreys (UVa), and J. Wall (Oxford

    A Radio Perspective on Star-Formation in Distant Galaxies

    Get PDF
    Determination of the epoch dependent star-formation rate of field galaxies is one of the principal goals of modern observational cosmology. Deep radio surveys, sensitive to starbursts out to zz \sim 1-2, may hold the key to understanding the evolution of the starburst phenonemon unhindered by the effects of dust. Using deep, high resolution radio observations of the Hubble Deep Field, we show that the μ\muJy radio emission from field galaxies at z0.41z\sim 0.4-1 is primarily starburst in origin. In addition, we have discovered a population of optically faint, possibly obscured systems that are candidate high-zz protogalaxies. At least one of these radio sources is identified with a sub-mm detection.Comment: 4 pages, 3 figs., paper presented at Maryland October Astrophysics Conference, 'Before the Dark Ages: When the Galaxies were Young

    Supporting Knitwear Design Using Case-Based Reasoning

    Get PDF
    Organised by: Cranfield UniversityKnitwear design is a creative activity that is hard to automate using the computer. The production of the associated knitting pattern, however, is repetitive, time-consuming and error-prone, calling for automation. Our objectives are two-fold: to facilitate the design and to ease the burden of calculations and checks in pattern production. We conduct a feasibility study for applying case-based reasoning in knitwear design: we describe appropriate methods and show how they can be implemented.Mori Seiki – The Machine Tool Compan

    Radar signature determination: Trends and limitations

    Get PDF
    Modelling studies, as means for assessing what could be called radar signatures, are a part of two radar remote sensing research programs with which the author is affiliated. First, at the University of New South Wales, assessment of SIR-B data is being undertaken for a number of purposes including its value in arid land geomorphological and geological studies, forest and crop assessment, and mapping. A number of early results have been reported, however modelling aspects are still at an early stage. Secondly, the author recently spent 6 months working on SIR-B invertible forest canopy modelling in the Department of Geography at the University of California, Santa Barbara. Results from this work are outlined

    Mainstream parallel array programming on cell

    Get PDF
    We present the E] compiler and runtime library for the ‘F’ subset of the Fortran 95 programming language. ‘F’ provides first-class support for arrays, allowing E] to implicitly evaluate array expressions in parallel using the SPU coprocessors of the Cell Broadband Engine. We present performance results from four benchmarks that all demonstrate absolute speedups over equivalent ‘C’ or Fortran versions running on the PPU host processor. A significant benefit of this straightforward approach is that a serial implementation of any code is always available, providing code longevity, and a familiar development paradigm

    Tourette syndrome research highlights 2015 [version 1; referees: 3 approved]

    Get PDF
    We present selected highlights from research that appeared during 2015 on Tourette syndrome and other tic disorders. Topics include phenomenology, comorbidities, developmental course, genetics, animal models, neuroimaging, electrophysiology, pharmacology, and treatment. We briefly summarize articles whose results we believe may lead to new treatments, additional research or modifications in current models of TS