Sourcing Olive Jars Using U‐Pb Ages of Detrital Zircons: A Study of 16th Century Olive Jars Recovered from the Solomon Islands     

Sarah J. Kelloway  Steven Craven  Mark Pecha  William R. Dickinson  Martin Gibbs  Timothy Ferguson  Michael D. Glascock 《Geoarchaeology》2014,29(1):47-60

We present U‐Pb ages of zircons extracted from olive jars recovered from two sites associated with Alvaro de Mendaña y Neyra's colonising expedition to the Solomon Islands, c. 1595–1596 A.D. The olive jars were previously associated with Panamanian and Peruvian origins based on petrological and geochemical studies. To further define provenance, 143 zircons were extracted from five olive jar sherds, analyzed and dated. The resultant U‐Pb ages range from the Archaean to the Cenozoic (2977.2 ± 29.0–3.2 ± 4.0 Ma), but the dominance of Cretaceous and Palaeogene ages (∼ 90% of the total age population is between ∼ 145 and 23 Ma) supports a Peruvian origin based on comparative geology, with the Coastal Batholith of Peru a prime candidate area of ceramic production. These results are significant for the characterization of 16th Century Peruvian‐made pottery and our understanding of its production and trade.  相似文献   

One ring to encompass them all: a giant stellar structure that surrounds the Galaxy     

R. A. Ibata  M. J. Irwin  G. F. Lewis  A. M. N. Ferguson  N. Tanvir 《Monthly notices of the Royal Astronomical Society》2003,340(3):L21-L27

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A new population of extended, luminous star clusters in the halo of M31     

A. P. Huxor  N. R. Tanvir  M. J. Irwin  R. Ibata  J. L. Collett  A. M. N. Ferguson  T. Bridges  G. F. Lewis 《Monthly notices of the Royal Astronomical Society》2005,360(3):1007-1012

We present three new clusters discovered in the halo of M31 which, although having globular-like colours and luminosities, have unusually large half-light radii, ∼30 pc. They lie at projected galactocentric distances of ≈15 to ≈35 kpc. These objects begin to fill the gap in parameter space between globular clusters and dwarf spheroidals, and are unlike any clusters found in the Milky Way, or elsewhere to date. Colour–magnitude diagrams, integrated photometric properties and derived King profile fit parameters are given, and we discuss possible origins of these clusters and their relationships to other populations.  相似文献   

“Borehole temperatures, climate change and pre-observational surface air temperature mean: Allowance for hydraulic conditions” by Louise Bodri and Vladimir Cermak     

Grant Ferguson   《Global and Planetary Change》2005,48(4):313-314

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Galaxy Threshing and Ultra-Compact Dwarfs in the Fornax Cluster     

M.D. Gregg  M.J. Drinkwater  M.J. Hilker  Steven Phillipps  J. Bryn Jones  Henry C. Ferguson 《Astrophysics and Space Science》2003,285(1):113-117

We have discovered a new type of galaxy in the Fornax Cluster: `ultra-compact' dwarfs (UCDs). The UCDs are unresolved in ground-based imaging and have spectra typical of old stellar systems. Although the UCDs resemble overgrown globular clusters, based on VLT UVES echelle spectroscopy, they appear to be dynamically distinct systems with higher internal velocity dispersions and M/L ratios for a given luminosity than Milky Way or M31 globulars. Our preferred explanation for their origin is that they are the remnant nuclei of dwarf elliptical galaxies which have been tidally stripped, or `threshed' by repeated encounters with the central cluster galaxy, NGC1399. If correct, then tidal stripping of nucleated dwarfs to form UCDs may, over a Hubble time, be an important source of the plentiful globular cluster population in the halo of NGC1399, and, by implication, other cD galaxies. In this picture, the dwarf elliptical halo contents, up to 99% of the original dwarf luminosity, contribute a significant fraction of the populations of intergalactic stars, globulars, and gas in galaxy clusters. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Remedying the effects of array shape distortion on the spatialfiltering of acoustic data from a line array of hydrophones     

Ferguson  B.G. 《Oceanic Engineering, IEEE Journal of》1993,18(4):565-571

The effects of both small perturbations and large deformations to the array's shape on both conventional and adaptive beamformers are shown for two frequencies: the spatial Nyquist frequency (or design frequency) of the array and a frequency about three times greater. Large shape deformations lead to a decrease in the conventional beamformer's output power for a beam steered in the direction of the signal source, together with an increase in the sidelobe levels (or secondary maxima), while small perturbations in the array shape have little effect. Signal suppression is observed to be far greater for the adaptive beamformer because it is very sensitive to system errors. The imposition of a weight norm constraint on the adaptive beamformer reduces the signal suppression only for small shape perturbations array shape estimation techniques are needed to reduce signal suppression for large shape deformations. The adverse effects of a nonlinear array shape on both conventional and adaptive beamforming are shown to be substantially reduced by applying techniques that estimate the coordinates of the hydrophones prior to beamforming  相似文献   

The tidal trail of NGC 205?     

A. W. McConnachie  M. J. Irwin  G. F. Lewis  R. A. Ibata  S. C. Chapman  A. M. N. Ferguson  N. R. Tanvir 《Monthly notices of the Royal Astronomical Society》2004,351(4):L94-L98

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Star Formation in the Outskirts of Disk Galaxies     

Annette M.N. Ferguson 《Astrophysics and Space Science》2002,281(1-2):119-122

The far outer regions of galactic disks allow an important probe of both star formation and galaxy formation. I discuss how observations of HII regions in these low gas density, low metallicity environments can shed light on the physical processes which drive galactic star formation. The history of past star formation at large radii, as traced by observations of old and intermediate-age stars, constrains the epoch at which the highest angular momentum regions of disks were in place; first results for the M31 disk suggest this occured a significant (≳ 8 Gyr) time ago. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Uncertainty in 1D Heat‐Flow Analysis to Estimate Groundwater Discharge to a Stream     

Grant Ferguson  Victor Bense 《Ground water》2011,49(3):336-347

Temperature measurements have been used by a variety of researchers to gain insight into groundwater discharge patterns. However, much of this research has reduced the problem to heat and fluid flow in one dimension for ease of analysis. This approach is seemingly at odds with the goal of determining spatial variability in specific discharge, which implies that the temperature field will vary in more than one dimension. However, it is unclear how important the resulting discrepancies are in the context of determining groundwater discharge to surface water bodies. In this study, the importance of these variations is examined by testing two popular one‐dimensional analytical solutions with stochastic models of heat and fluid flow in a two‐dimensional porous medium. For cases with low degrees of heterogeneity in hydraulic conductivity, acceptable results are possible for specific discharges between 10^?7 and 10^?5 m/s. However, conduction into areas with specific discharges less than 10^?7 m/s from adjacent areas can lead to significant errors. In some of these cases, the one‐dimensional solutions produced estimates of specific discharge of nearly 10^?6 m/s. This phenomenon is more likely in situations with greater degrees of heterogeneity.  相似文献   

Non-stationarity of the signal and noise characteristics of seasonal precipitation anomalies     

Ian M. Ferguson  Philip B. Duffy  Thomas J. Phillips  Xu Liang  John A. Dracup  Siegfried Schubert  Philip Pegion 《Climate Dynamics》2011,36(3-4):739-752

In order to improve seasonal-to-interannual precipitation forecasts and their application by decision makers, there is a clear need to understand when, where, and to what extent seasonal precipitation anomalies are driven by potentially predictable surface–atmosphere interactions versus to chaotic interannual atmospheric dynamics. Using a simple Monte Carlo approach, interannual variability and linear trends in the SST-forced signal and potential predictability of boreal winter precipitation anomalies is examined in an ensemble of twentieth century AGCM simulations. Signal and potential predictability are shown to be non-stationary over more than 80% of the globe, while chaotic noise is shown to be stationary over most of the globe. Correlation analysis with respect to magnitudes of the four leading modes of global SST variability suggests that interannual variability and trends in signal and potential predictability over 35% of the globe is associated with ENSO-related SST variability; signal and potential predictability are not significantly associated with SST modes characterized by a global SST trend, North Atlantic SST variability, and North Pacific SST variability, respectively. Results suggest that mechanisms other than SST variability contribute to the non-stationarity of signal and noise characteristics of hydroclimatic variability over mid- and high-latitude regions.  相似文献