The Dominion Radio Astrophysical Observatory Galactic Plane Survey Pilot Project: The W3/W4/W5/HB 3 Region

The Dominion Radio Astrophysical Observatory, in collaboration with other sites, recently began a Galactic plane survey. The data from the pilot project for this survey are presented here. They cover the W3/W4/W5/HB 3 Galactic complex in the Perseus arm. Ten fields were observed to produce mosaic images of this region at two continuum frequencies, 408 and 1420 MHz, as well as in the 21 cm spectral line of atomic hydrogen at 127 velocities covering +55.5 to -153.9 km s-1. At 1420 MHz (continuum and spectral line), an area of approximately 8° × 6° (l × b) is imaged with a resolution of 100 × 114 (east-west by north-south) whereas, at 408 MHz, the coverage was 14° × 10° (l × b) with a resolution of 35 × 40 (east-west by north-south). The spectral-line data cube constitutes the highest resolution atomic hydrogen study of the entire complex to date. A wealth of large-scale filaments, arcs, bubbles, and shells is revealed

The HI shell G132.6-0.7-25.3: A Supernova Remnant or an Old Wind-Blown Bubble?

Data from the Canadian Galactic Plane Survey reveal an abundance of HI shells and arcs in the disk of our galaxy. While their shape is suggestive of stellar winds or supernovae influence, very few of these structures have been examined in detail thus far. A fine example is an HI shell in the outer Galaxy with no continuum counterpart discovered in the survey's pilot project. Its size and kinematics suggest that it was created by the winds of a single late-type O star which has since evolved off the main sequence or by a supernova explosion. A B1 Ia star at the centre of the shell, in projection, is a possible candidate for energy source if the shell is assumed to be wind-blown. The shell's shape implies a surprisingly small scale height of less than about 30 pc for the surrounding gas if the elongation is due to evolution in a density gradient.Comment: 25 pages, 6 figures. Accepted for publication in the Astronomical Journa

Probing the Interstellar Medium using HI absorption and emission towards the W3 HII region

HI spectra towards the W3 HII complex are presented and used to probe the Galactic structure and interstellar medium conditions between us and this region. The overall shape of the spectra is consistent with the predictions of the Two-Arm Spiral Shock model wherein the gas found in the -40 km/s to -50 km/s range has been accelerated by some 20 km/s from its rotation curve velocity. Spin temperatures of ~100 K are derived for the Local Arm gas, lower than found in a previous, similar study towards DR 7. For the interarm region, values on the order of 300 K are found, implying a negligible filling factor for the Cold Neutral Medium (<< 1%). Some of the absorbing gas at velocities near -40 km/s is confirmed to be associated with the HII regions.Comment: 23 pages, 6 figures, accepted for publication in the Astronomical Journa

Radio polarimetric imaging of the interstellar medium: magnetic field and diffuse ionized gas structure near the W3/W4/W5/HB3 complex

We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron background emission by Faraday rotation arising in foreground ionized gas having an emission measure as low as 1 cm^{-6} pc. Several new remarkable phenomena have been identified, including: mottled polarization arising from random fluctuations in a magneto-ionic screen that we identify with a medium in the Perseus Arm, probably in the vicinity of the HII regions themselves; depolarization arising from very high rotation measures (several times 10^3 rad m^{-2}) and rotation measure gradients due to the dense, turbulent environs of the HII regions; highly ordered features spanning up to several degrees; and an extended influence of the HII regions beyond the boundaries defined by earlier observations. In particular, the effects of an extended, low-density ionized halo around the HII region W4 are evident, probably an example of the extended HII envelopes postulated as the origin of weak recombination-line emission detected from the Galactic ridge. Our polarization observations can be understood if the uniform magnetic field component in this envelope scales with the square-root of electron density and is 20 microG at the edge of the depolarized region around W4, although this is probably an over-estimate since the random field component will have a significant effect.Comment: 18 pages, 8 figures (7 jpeg and 1 postscript), accepted for publication in the Astrophysical Journa

Three-Dimensional Simulations of Magnetized Superbubbles: New Insights into the Importance of MHD Effects on Observed Quantities

We present three-dimensional magnetohydrodynamic (MHD) simulations of superbubbles, to study the importance of MHD effects in the interpretation of images from recent surveys of the Galactic plane. These simulations focus mainly on atmospheres defined by an exponential density distribution and the Dickey & Lockman (1990) density distribution. In each case, the magnetic field is parallel to the Galactic plane and we investigate cases with either infinite scale height (constant magnetic field) or a constant ratio of gas pressure to magnetic pressure. The three-dimensional structure of superbubbles in these simulations is discussed with emphasis on the axial ratio of the cavity as a function of magnetic field strength and the age of the bubble. We investigate systematic errors in the age of the bubble and scale height of the surrounding medium that may be introduced by modeling the data with purely hydrodynamic models. Age estimates derived with symmetric hydrodynamic models fitted to an asymmetric magnetized superbubble can differ by up to a factor of four, depending on the direction of the line of sight. The scale height of the surrounding medium based on the Kompaneets model may be up to 50% lower than the actual scale height. We also present the first ever predictions of Faraday rotation by a magnetized superbubble based on three-dimensional MHD simulations. We emphasize the importance of MHD effects in the interpretation of observations of superbubbles.Comment: 21 journal pages. 17 figures. 5 tables (added extensive discussion on the effect of cooling on the bubbles); Accepted for publications in the Astrophysical Journal. Related animations can be accessed via http://www.capca.ucalgary.c

Spider silk protein structure analysis by FTIR and STXM spectromicroscopy techniques

Spider silk displays incredible strength and elas¬ticity for its size and weight.[1] These properties have sparked interest in determining the protein structures of the silk fibers allowing for the pro¬duction of synthetic silks.[2] This study compares the mid-infrared (Mid IR) spectra of silk from five different spider species to investigate the com-monalities between species and web type. The results demonstrate the Mid IR spectra from all types of spider silk to be similar, showing protein peaks in the Amide I and II regions. To study the environmental effects of the acid solution on the silk protein structure, two of the five species’ silk: Black & Yellow Orb Weaver (Argiope aurantia) and Black Widow (Latrodectus hesperus), were exposed to either rain water or 0.001 M sulphuric acid solution, similar to acid rain in pH. Spectra obtained at the Mid IR beamline and the data obtained from the X-ray Absorption Near Edge Spectroscopy (XANES) were compared for these samples to see the effect of the acid rain-like solu¬tion on the silk proteins. No conclusive evidence from the data is present to suggest that the acid rain solution had an effect on the protein structures of either type of spider silk.La soie d’araignée est à la fois robuste et flexible pour sa taille et son poids.[1] Ces propriétés ont piqué la curiosité de déterminer la structure des protéines des fibres de soie qui pourrait permettre éventuelle¬ment la production des soies synthétiques.[2] Cette étude compare les spectres mi- infrarouges (Mi IR) de soie de cinq espèces différentes d’araignée afin de trouver des similitudes entre les espèces et les genres de toiles. Les résultats démontrent que les spectres mi- infrarouges de tout type de soie d’araignée étudié sont similaires, présentant des apogées de protéines dans les régions de l’Amide I et II. Afin d’étudier les effets environnementaux d’une solution acide sur la structure de la proté¬ine de soie, la soie de deux des cinq espèces, le orbe tisserand noir et jaune (Argiope aurantia) et la veuve noire (Latrodectus Hesperus), ont été expo¬sé soit à la pluie naturelle soit à une solution d’acide sulfurique 0.001 M qui est proche au pH de la pluie acide. Les spectres obtenus à l’onde dirigée Mi IR et les données obtenues de l’absorption de la radi¬ographie près du seuil de la spectroscopie (ARSS) ont été comparés de ces échantillons afin de con¬stater l’effet de la solution d’acide sulfurique sur des protéines de soie. Il n’y avait aucune preuve probante des données suggérant que la solution d’acide sulfurique avait un effet sur la structure des protéines de soie des araignées étudié