86 GHz Very Long Baseline Polarimetry of 3C273 and 3C279 with the Coordinated Millimeter VLBI Array

86 GHz Very Long Baseline Polarimetry probes magnetic field structures within the cores of Active Galactic Nuclei at higher angular resolutions and a spectral octave higher than previously achievable. Observations of 3C273 and 3C279 taken in April 2000 with the Coordinated Millimeter VLBI Array have resulted in the first total intensity (Stokes I) and linear polarization VLBI images reported of any source at 86 GHz. These results reveal the 86 GHz electric vector position angles within the jets of 3C273 and 3C279 to be orthogonal to each other, and the core of 3C273 to be unpolarized. If this lack of polarization is due to Faraday depolarization alone, the dispersion in rotation measure is >=90000 rad/m^2 for the core of 3C273.Comment: AASTeX v5.02; 10 pages; 4 figures; accepted for publication in the Astrophysical Journal Letter

On the depolarization of discrete radio sources by faraday dispersion technical report no. 440

Discrete radio source depolarization by Faraday dispersio

The COINS Sample - VLBA Identifications of Compact Symmetric Objects

We present results of multifrequency polarimetric VLBA observations of 34 compact radio sources. The observations are part of a large survey undertaken to identify CSOs Observed in the Northern Sky (COINS). Compact Symmetric Objects (CSOs) are of particular interest in the study of the physics and evolution of active galaxies. Based on VLBI continuum surveys of ~2000 compact radio sources, we have defined a sample of 52 CSOs and CSO candidates. In this paper, we identify 18 previously known CSOs, and introduce 33 new CSO candidates. We present continuum images at several frequencies and, where possible, images of the polarized flux density and spectral index distributions for the 33 new candidates and one previously known but unconfirmed source. We find evidence to support the inclusion of 10 of these condidates into the class of CSOs. Thirteen candidates, including the previously unconfirmed source, have been ruled out. Eleven sources require further investigation. The addition of the 10 new confirmed CSOs increases the size of this class of objects by 50%.Comment: 24 pages, incl 8 figures. Accepted for publication in ApJ. Figure quality degraded in the interests of space, full gzipped PS version also available at http://www.ee.nmt.edu/~apeck/papers

Toponymy of Herschel Island (Qikiqtaryuk), Western Arctic Coast, Canada

The official names for several of the features on Herschel Island are derived from the visit to the island by USS Thetis, Lt. Cdr. Charles Stockton commanding, on 15 – 16 August 1889. In 24 hours, Stockton and his crew surveyed the coast sufficiently to compile and publish a map, which included the bathymetry of Pauline Cove and the strait between the island and the mainland, now called Workboat Passage. Stockton named features after two whaling ships that were in the vicinity when he arrived (Orca and Thrasher), his own Thetis, his wife (Pauline Lethilhon King), three ensigns to whom he assigned bathymetric surveys (Robert Lopez, Edward Simpson, and Rogers Wells, Jr.), two of his other officers (Lt. Arthur Osborn and Ensign John Bell), and an officer of the Royal Navy (Capt. Sir Richard Collinson). Only one feature, Avadlek Spit, has an Inuvialuktun official name.Le nom officiel de plusieurs des accidents géographiques de l’île Herschel découle de la visite de l’île par le capitaine de corvette Charles Stockton en tête du USS Thetis, les 15 et 16 août 1889. En 24 heures, Charles Stockton et les membres de son équipage ont fait des levés de la côte suffisamment approfondis pour pouvoir compiler et publier une carte, qui comprenait notamment la bathymétrie de l’anse Pauline et le détroit séparant l’île de la terre ferme, qui porte maintenant le nom de Workboat Passage. Charles Stockton a nommé les accidents géographiques d’après deux baleiniers qui se trouvaient dans les environs à leur arrivée (Orca et Thrasher), ainsi que d’après son propre bateau, soit le Thetis, sa femme (Pauline Lethilhon King), trois porte-étendards auxquels les levés bathymétriques avaient été confiés (Robert Lopez, Edward Simpson et Rogers Wells, fils), deux de ses autres officiers (le lieutenant Arthur Osborn et le porte-étendard John Bell) et un officier de la Marine royale (le capitaine Sir Richard Collinson). Un seul accident géographique, soit l’Avadlek Spit, porte un nom inuvialuktun officiel

Concurrent 43 and 86 GHz Very Long Baseline Polarimetry of 3C273

We present sub-milliarcsecond resolution total intensity and linear polarization VLBI images of 3C273, using concurrent 43 and 86 GHz data taken with the Very Long Baseline Array in May 2002. The structure seen in the innermost jet suggest that we have fortuitously caught the jet in the act of changing direction. The polarization images confirm that the core is unpolarized (fractional polarization m < 1 %) at 86 GHz, but also show well ordered magnetic fields (m ~ 15 %) in the inner jet, at a projected distance of 2.3 pc from the core. In this strongly polarized region, the rotation measure changes across the jet by 4.2 x 10^{4} rad m^{-2} over an angular width of about 0.3 milliarcseconds. If the lack of polarization in the core is also attributed to a Faraday screen, then a rotation measure dispersion > 5.2 x 10^{4} rad m^{-2} must be present in or in front of that region. These are among the highest rotation measures reported so far in the nucleus of any active galaxy or quasar, and must occur outside (but probably close to) the radio emitting region. The transverse rotation measure gradient is in the same sense as that observed by Asada et al and by Zavala and Taylor at greater core distances. The magnitude of the transverse gradient decreases rapidly with distance down the jet, and appears to be variable.Comment: 4 pages, LaTeX, 3 postscript figures, submitted to Astrophysical Journal Letter

Game-Making as a means to deliver the new Computing curriculum in England

Integrating digital technologies into the curriculum has been a growing challenge, especially due to the failures of the majority of initiatives that were envisioned for this purpose. In an effort to comprehend and solve these issues, England has recently proposed a shift in the curricular approach, focusing in teaching technology's conceptual basis rather than technological applications. Thus, the new National Curriculum in England, valid in 2014, focuses on the development of new concepts and the empowerment of the students towards information and communication technologies (ICT). This article presents these recent discussions in the curricular field related to ICT/Computing teaching. It also describes an empirical experience carried out in England, in which students from primary schools explored game-making activities through computational and media culture perspectives as a means to promote this new curriculum. The results obtained through this preliminary research show that, although using digital games to connect Computing, Media and Arts in Education could be regarded as a complex activity, this is a possible path to reach the objectives outlined by the new National Curriculum

Extragalactic Zeeman Detections in OH Megamasers

We have measured the Zeeman splitting of OH megamaser emission at 1667 MHz from five (ultra)luminous infrared galaxies ([U]LIRGs) using the 305 m Arecibo telescope and the 100 m Green Bank Telescope. Five of eight targeted galaxies show significant Zeeman-splitting detections, with 14 individual masing components detected and line-of-sight magnetic field strengths ranging from ~0.5-18 mG. The detected field strengths are similar to those measured in Galactic OH masers, suggesting that the local process of massive star formation occurs under similar conditions in (U)LIRGs and the Galaxy, in spite of the vastly different large-scale environments. Our measured field strengths are also similar to magnetic field strengths in (U)LIRGs inferred from synchrotron observations, implying that milligauss magnetic fields likely pervade most phases of the interstellar medium in (U)LIRGs. These results provide a promising new tool for probing the astrophysics of distant galaxies.Comment: 32 pages, 14 figures, 8 tables. Accepted for publication in The Astrophysical Journal v680n2, June 20, 2008; corrected 2 typo

The effect of image fractal properties and its interaction with visual discomfort on gait kinematics

Exposure to images of urban environments affords higher cognitive processing demands than exposure to images of nature scenes; an effect potentially related to differences in low-level image statistics such as fractals. The aim of the current study was to investigate whether the fractal dimensions of an abstract scene affect cognitive processing demands, using gait kinematics as a measure of cognitive demand. Participants (n = 40) were asked to walk towards different types of synthetic images which were parametrically varied in their fractal dimensions. At the end of each walk, participants rated each image for its visual discomfort (n = 20) or for its likability (n = 20) as potential confounding factors. Fractal dimensions were predictors of walking speed. Moreover, the interaction between fractal dimensions and subjective visual discomfort but not liking predicted velocity. Overall, these data suggest that fractal dimensions indeed contribute to environmentally induced cognitive processing demands

Measurement of the Integrated Faraday Rotations of BL Lac Objects

We present the results of multi-frequency polarization VLA observations of radio sources from the complete sample of northern, radio-bright BL Lac objects compiled by H. Kuhr and G. Schmidt. These were used to determine the integrated rotation measures of 18 objects, 15 of which had never been measured previously, which hindered analysis of the intrinsic polarization properties of objects in the complete sample. These measurements make it possible to correct the observed orientations of the linear polarizations of these sources for the effect of Faraday rotation. The most probable origin for Faraday rotation in these objects is the Galactic interstellar medium. The results presented complete measurements of the integrated rotation measures for all 34 sources in the complete sample of BL Lac objects.Comment: 9 pages, 7 figure

A View through Faraday's Fog 2: Parsec Scale Rotation Measures in 40 AGN

Results from a survey of the parsec scale Faraday rotation measure properties for 40 quasars, radio galaxies and BL Lac objects are presented. Core rotation measures for quasars vary from approximately 500 to several thousand radians per meter squared. Quasar jets have rotation measures which are typically 500 radians per meter squared or less. The cores and jets of the BL Lac objects have rotation measures similar to those found in quasar jets. The jets of radio galaxies exhibit a range of rotation measures from a few hundred radians per meter squared to almost 10,000 radians per meter squared for the jet of M87. Radio galaxy cores are generally depolarized, and only one of four radio galaxies (3C-120) has a detectable rotation measure in the core. Several potential identities for the foreground Faraday screen are considered and we believe the most promising candidate for all the AGN types considered is a screen in close proximity to the jet. This constrains the path length to approximately 10 parsecs, and magnetic field strengths of approximately 1 microGauss can account for the observed rotation measures. For 27 out of 34 quasars and BL Lacs their optically thick cores have good agreement to a lambda squared law. This requires the different tau = 1 surfaces to have the same intrinsic polarization angle independent of frequency and distance from the black hole.Comment: Accepted to the Astrophysical Journal: 71 pages, 40 figure