CLASS B0445+123: a new two-image gravitational lens system     

M. K. Argo  N. J. Jackson  I. W. A. Browne  T. York  J. P. McKean  A. D. Biggs  R. D. Blandford  A. G. de Bruyn  K. H. Chae  C. D. Fassnacht  L. V. E. Koopmans  S. T. Myers  M. Norbury  T. J. Pearson  P. M. Phillips  A. C. S. Readhead  D. Rusin  P. N. Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,338(4):957-961

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Chemical Telemetry of OH Observed to Measure Interstellar Magnetic Fields     

Dr Serena Viti PhD  Thomas W. Hartquist  Philip C. Myers 《Astrophysics and Space Science》2006,302(1-4):109-115

We present models for the chemistry in gas moving towards the ionization front of an HII region. When it is far from the ionization front, the gas is highly depleted of elements more massive than helium. However, as it approaches the ionization front, ices are destroyed and species formed on the grain surfaces are injected into the gas phase. Photodissociation removes gas phase molecular species as the gas flows towards the ionization front. We identify models for which the OH column densities are comparable to those measured in observations undertaken to study the magnetic fields in star forming regions and give results for the column densities of other species that should be abundant if the observed OH arises through a combination of the liberation of H₂O from surfaces and photodissociation. They include CH₃OH, H₂CO, and H₂S. Observations of these other species may help establish the nature of the OH spatial distribution in the clouds, which is important for the interpretation of the magnetic field results.  相似文献   

The 2dF–SDSS LRG and QSO (2SLAQ) Survey: the z < 2.1 quasar luminosity function from 5645 quasars to g= 21.85     

Gordon T. Richards  Scott M. Croom  Scott F. Anderson  Joss Bland-Hawthorn  Brian J. Boyle  Roberto De Propris  Michael J. Drinkwater  Xiaohui Fan  James E. Gunn  &#;eljko Ivezi&#;  Sebastian Jester  Jon Loveday  Avery Meiksin  Lance Miller  Adam Myers  Robert C. Nichol  Phil J. Outram  Kevin A. Pimbblet  Isaac G. Roseboom  Nic Ross  Donald P. Schneider  Tom Shanks  Robert G. Sharp  Chris Stoughton  Michael A. Strauss  Alexander S. Szalay  Daniel E. Vanden Berk  Donald G. York 《Monthly notices of the Royal Astronomical Society》2005,360(3):839-852

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Galaxy evolution: Inhomogeneous halo collapse     

Jeannette M. Myers  Dieter H. Hartmann  Lih-Sin The 《Astrophysics and Space Science》2003,284(2):787-790

In an effort to study the halo globular clusters we perform a simulation of inhomogeneous halo collapse using a SPH/N-body code. We include dark matter particles, (cooling) gas, and stars. Supernova feedback is included as a heat source for the gas in the local environment of star forming regions. We find this model cannot reproduce the age distribution and spatial distribution of halo globular clusters. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

On The Internal Structure Of Starless Cores. Physical and Chemical Properties of L1498 and L1517B     

M. Tafalla  P.C. Myers  P. Caselli  C.M. Walmsley 《Astrophysics and Space Science》2004,292(1-4):347-354

We have characterized the internal structure of two close-to-round starless cores in Taurus, L1498 and L1517B, setting constraints on the initial conditions of star formation and on models of core condensation. Our analysis is based on high angular resolution observations in at least two transitions of NH₃, N₂H⁺, CS, C³⁴S, C¹⁸O, and C¹⁷O, together with maps of the 1.2 mm continuum. For both cores, we derive radial profiles of constant temperature and constant turbulence, and density distributions close to those of non-singular isothermal spheres. Using a Monte Carlo radiative transfer model, we derive abundance profiles for all species and find a pattern of strong chemical differentiation. NH₃ has a higher abundance toward the core centers while N₂H⁺ has a constant abundance over most of the cores. Both C¹⁸O and CS (and isotopomers) are strongly depleted in the core interiors, most likely due to their freeze out onto cold dust grains. Concerning the kinematics of the dense gas, we find (in addition to constant turbulence) a pattern of internal motions at the level of 0.05 km s^?1. These motions seem correlated with asymmetries in the pattern of molecular depletion, and we interpret them as residuals of core contraction. Their distribution and size suggest that core formation happens in rather irregular manner. A comparison with supersonic turbulence models of core formation shows that our observed cores are much more quiescent than allowed by these models.  相似文献   

An iras atlas of ysos in nearby dark clouds     

D. O. S. Wood  P. C. Myers 《Astrophysics and Space Science》1995,224(1-2):199-202

We are using the newIRAS Sky Survey Atlas to construct a catalog of Galactic dark clouds and their associated Young Stellar Objects (YSOs). FromIRAS 100 and 60µm data we calculate images of the 100µm optical depth distribution in the clouds. Using theIRAS Faint Source Catalog we identify sources which have colors indicative of YSOs and have positions that lie inside cloud boundaries in the optical depth images. Here we present some preliminary results of applying this analysis to the Chamaeleon dark cloud complex.  相似文献   

Evidence for an extended Sunyaev–Zel'dovich effect in WMAP data     

A. D. Myers  T. Shanks  P. J. Outram  W. J. Frith  A. W. Wolfendale 《Monthly notices of the Royal Astronomical Society》2004,347(4):L67-L72

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The Kwakshua Watersheds Observatory,central coast of British Columbia,Canada     

Ian J. W. Giesbrecht  William C. Floyd  Suzanne E. Tank  Ken P. Lertzman  Brian P. V. Hunt  Maartje C. Korver  Allison A. Oliver  Ray Brunsting  Paul Sanborn  Santiago G. Gonzalez Arriola  Gordon W. Frazer  Kyra A. St. Pierre  Shawn Hateley  James McPhail  Colby Owen  Stewart Butler  Bryn Fedje  Emma Myers  Lucy Quayle  Emily Haughton  Isabelle Desmarais  Rob White  David J. Levy-Booth  Colleen T. E. Kellogg  Jennifer M. Jackson  William W. Mohn  Steven J. Hallam  Justin Del Bel Belluz 《水文研究》2021,35(6):e14198

The Kwakshua Watersheds Observatory (KWO) is an integrative watersheds observatory on the coastal margin of a rain-dominated bog-forest landscape in British Columbia (BC), Canada. Established in 2013, the goal of the KWO is to understand and model the flux of terrestrial materials from land to sea – the origins, pathways, processes and ecosystem consequences – in the context of long-term environmental change. The KWO consists of seven gauged watersheds and a network of observation sites spanning from land to sea and along drainage gradients within catchments. Time-series datasets include year-round measurements of weather, soil hydrology, streamflow, aquatic biogeochemistry, microbial ecology and nearshore oceanographic conditions. Sensor measurements are recorded every 5 min and water samples are collected approximately monthly. Additional observations are made during high-flow conditions. We used remote sensing to map watershed terrain, drainage networks, soils and terrestrial ecosystems. The watersheds range in size from 3.2 to 12.8 km², with varying catchment characteristics that influence hydrological and biogeochemical responses. Despite local variation, the overall study area is a global hotspot for yields of dissolved organic carbon, dissolved organic nitrogen and dissolved iron at the coastal margin. This observatory helps fill an important gap in the global network of observatories, in terms of spatial location (central coast of BC), climate (temperate oceanic), hydrology (very high runoff, pluvial regime), geology (igneous intrusive, glacially scoured), vegetation (bog rainforest) and soils (large stores of organic carbon).  相似文献   

Using Simultaneous Diagonalization to Identify a Space–Time Linear Coregionalization Model     

S. De Iaco  D. E. Myers  M. Palma  D. Posa 《Mathematical Geosciences》2013,45(1):69-86

Although there are multiple methods for modeling matrix covariance functions and matrix variograms in the geostatistical literature, the linear coregionalization model is still widely used. In particular it is easy to check to ensure whether the matrix covariance function is positive definite or that the matrix variogram is conditionally negative definite. One of the difficulties in using a linear coregionalization model is in determining the number of basic structures and the corresponding covariance functions or variograms. In this paper, a new procedure is given for identifying the basic structures of the space–time linear coregionalization model and modeling the matrix variogram. This procedure is based on the near simultaneous diagonalization of the sample matrix variograms computed for a set of spatiotemporal lags. A case study using a multivariate spatiotemporal data set provided by the Environmental Protection Agency of Lombardy, Italy, illustrates how nearly simultaneous diagonalization of the empirical matrix variograms simplifies modeling of the matrix variograms. The new methodology is compared with a previous one by analyzing various indices and statistics.  相似文献   

Sea-Ice Concentration Multivariate Assimilation for the Canadian East Coast in a Coupled Sea Ice–Ocean Model     

Anna Katavouta  Paul G. Myers 《大气与海洋》2014,52(5):418-433

The present study focuses on the impact of ocean state (i.e., salinity and temperature) updates on the sea-ice analysis and short-term forecast in an assimilative sea ice–ocean coupled system. A relatively simple sea-ice assimilation scheme was applied to the sea ice–ocean coupled North Atlantic Nucleus for European Modelling of the Ocean (NEMO) system with a focus on the Canadian East Coast. In this assimilation scheme the ocean state was updated directly based on the correlations between the model's sea-ice concentration and the upper ocean salinity and temperature. These correlations were based on a limited time ensemble generated by applying random perturbations to the atmospheric forcing fields. High deviations in the sea-ice conditions were found along the ice edge, implying that the sea-ice edge position is sensitive to small atmospheric forcing variations. Assimilation runs with and without ocean state updates (i.e., sea-ice concentration nudging) were conducted and compared for the winter of 2002. Both continuous and intermittent assimilation schemes were examined. In a continuous sea-ice assimilation experiment, the ocean direct update is unnecessary. When the sea-ice updates are introduced intermittently the ocean state has to be altered to accommodate them, or they will be rapidly diminished by the model's dynamics. The correlations between sea-ice concentration and ocean salinity and temperature based on the first 15 days of January were used for corrections during the entire winter season when, in addition to thermodynamic processes, dynamic processes are responsible for, and even dominate, sea-ice evolution on the Labrador and Newfoundland shelves. This was an adequate choice as was demonstrated by the results of the study which showed that the experiments with ocean state adjustments generated more accurate short-term sea-ice forecasts.  相似文献