Mapping the roots of the galactic outflow in NGC1569     

Mark S. Westmoquette  Linda J. Smith  Jay S. Gallagher III  Katrina M. Exter 《Astrophysics and Space Science》2009,324(2-4):187-193

The exact nature of the interaction between hot, fast-flowing star-cluster winds and the surrounding clumpy interstellar medium (ISM) in starburst galaxies has very few observational constraints. Besides furthering our knowledge of ISM dynamics, detailed observations of ionised gas at the very roots of large-scale outflows are required to place limits on the current generation of high-resolution galactic wind models. To this end, we conduct a detailed investigation of the ionised gas environment surrounding the young star clusters in the starburst galaxy NGC1569. Using high spatial and spectral-resolution Gemini/GMOS integral-field unit observations, we accurately characterise the line-profile shapes of the optical nebular emission lines and find a ubiquitous broad (～300 km?s^?1) component underlying a bright narrower component. By mapping the properties of the individual line components, we find correlations that suggest that the broad component results from powerful cluster wind–gas clump interactions. We propose a model to explain the properties of the line components and the general turbulent state of the ISM.  相似文献   

Eocene–Miocene carbon-isotope and floral record from brown coal seams in the Gippsland Basin of southeast Australia     

Guy R. Holdgate  Brian McGowran  Tom Fromhold  Barbara E. Wagstaff  Stephen J. Gallagher  Malcolm W. Wallace  Ian R.K. Sluiter  Michael Whitelaw 《Global and Planetary Change》2009,65(1-2):89-103

The carbon-isotope and palynological record through 580 m thick almost continuous brown coal in southeast Australia's Gippsland Basin is a relatively comprehensive southern hemisphere Middle Eocene to Middle Miocene record for terrestrial change. The carbon isotope δ¹³C_coal values of these coals range from ? 27.7‰ to ? 23.2. This isotopic variability follows gymnosperm/angiosperm fluctuations, where higher ratios coincide with heavier δ¹³C values. There is also long-term variability in carbon isotopes through time. From the Eocene greenhouse world of high gymnosperm-heavier δ¹³C_coal values, there is a progressive shift to lighter δ¹³C_coal values that follows the earliest (Oi1?) glacial events around 33 Ma (Early Oligocene). The overlying Oligocene–Early Miocene brown coals have lower gymnosperm abundance, associated with increased %Nothofagus (angiosperm), and lightening of isotopes during Oligocene cooler conditions.The Miocene palynological and carbon-isotope record supports a continuation to the Oligocene trends until around the late Early Miocene (circa 19 Ma) when a warming commenced, followed by an even stronger isotope shift around 16 Ma that peaked in the Middle Miocene when higher gymnosperm abundance and heavier isotopes prevailed. The cycle between the two major warm peaks of Middle Eocene and Middle Miocene was circa 30 Ma long. This change corresponds to a fall in inferred pCO₂ levels for the same period. The Gippsland data suggest a link between gymnosperm abundance, long-term plant δ¹³C composition, climatic change, and atmospheric pCO₂. Climatic deterioration in the Late Miocene terminated peat accumulation in the Gippsland Basin and no further significant coals formed in southeast Australia.The poor correspondence between this terrestrial isotope data and the marine isotope record is explained by the dominant control on δ¹³C by the gymnosperm/angiosperm abundance, although in turn this poor correspondence may reflect palaeoclimate control. From the brown coal seam dating, the coal appears to have accumulated during a considerable part of the allocated 30 Ma Cenozoic time period. These brown coal carbon isotope and palynological data appear to record a more gradual atmospheric carbon isotope change compared to the marine record.  相似文献   

Historic nutrient loading and recent species invasions caused shifts in water quality and zooplankton demography in two Finger Lakes (New York, USA)     

Meghan E. Brown  Tara M. Curtin  Corey J. Gallagher  John D. Halfman 《Journal of Paleolimnology》2012,48(3):623-639

We investigated the paleolimnology of Owasco and Seneca Lakes (New York, USA) and compiled water-quality monitoring data to describe environmental change during the past two centuries. Trophic shifts were detected in the oligotrophic to mesotrophic range and were likely driven by nutrient loading and species invasion. Based on box core reconstructions, primary production increased in both lakes during the last century, which is evidenced by the amount, type and isotopic composition of material preserved in the sediment. Organic matter accumulation and its stable carbon isotopic composition, as well as carbonate abundance, began to increase during the 1960s in Owasco Lake and the 1850s in Seneca Lake. Further, the abundance of phytoplanktivorous cladocera subfossils increased beginning in the 1910s in Seneca Lake and in the 1960s in Owasco Lake. The different timing and magnitude of the trophic shifts likely resulted from contrasts in lake residence time and species assemblages between the two lakes. The increases in primary and secondary production paralleled, and are interpreted to reflect, increased allochthonous nutrient loading. However, nutrient loading was not detected in the water-quality data, perhaps because of strong uptake of phosphates by phytoplankton or due to limited data collection. Rapid changes in cladoceran subfossils and water quality were also detected during the last decade. Concurrent with the establishment of non-native Cercopagis pengoi (fishhook waterflea), phytoplanktivorous cladocera remains declined, and the mucrone length of Bosmina increased, consistent with predictions of increased invertebrate predation. Additionally, the post-1990 decline in sediment carbonate, increased Secchi depth and decreased chlorophyll a concentrations followed the establishment of filter-feeding Dreissena spp. (zebra and quagga mussels). Collectively, paleolimnological data and water-quality monitoring provided a more complete and consistent record of shifts in the productivity of Owasco and Seneca Lakes, which were useful to understand environmental changes over different time scales. Physical, geochemical and biological changes were temporally consistent among three cores collected from different locations in each lake, but differed in magnitude for several variables (e.g., grain size and cladoceran subfossils), which could reflect near-shore to offshore gradients.  相似文献   

Multiscale Analysis of Active Region Evolution     

R. J. Hewett  P. T. Gallagher  R. T. J. McAteer  C. A. Young  J. Ireland  P. A. Conlon  K. Maguire 《Solar physics》2008,248(2):311-322

Flows in the photosphere of solar active regions are turbulent in nature. Because magnetic fields are frozen into the plasma on the solar surface, magnetograms can be used to investigate the processes responsible for structuring active regions. Here, a continuous wavelet technique is developed, analyzed, and used to investigate the multiscale structure of an evolving active region using magnetograms obtained by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). The multiscale structure was measured using a 2D continuous wavelet technique to extract the energy spectrum of the region over the time scale of 13 days. Preliminary evidence of an inverse cascade in active region NOAA 10488 is presented as well as a potential relationship between energy scaling and flare productivity.  相似文献   

Performance of Major Flare Watches from the Max Millennium Program (2001 – 2010)     

D. S. Bloomfield  P. T. Gallagher  W. H. Marquette  R. O. Milligan  R. C. Canfield 《Solar physics》2016,291(2):411-427

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Nitrogen Pools of Macrophyte Species in a Coastal Lagoon Salt Marsh: Implications for Seasonal Storage and Dispersal     

Tracy Elsey-Quirk  Denise M. Seliskar  John L. Gallagher 《Estuaries and Coasts》2011,34(3):470-482

High nitrogen (N) loading rates received by coastal bays can have deleterious effects on aquatic ecosystems. Salt marshes can intercept land-based N through seasonal plant uptake, denitrification, and burial. Salt marshes fringing Delaware’s Inland Bays are characterized by different plant species occurring in close proximity. To evaluate N pool retention and loss for the dominant plant species, we measured seasonal N concentration and pool size, N resorption efficiency, loss during decomposition, and soil N. Seasonal variation in N pools and fluxes differed among species. Seasonal differences in the total N pools of the herbaceous species were largely influenced by belowground fine root and dead macro-organic matter fluxes. N production rate estimates ranged from 18 g N m⁻² year⁻¹ aboveground for the high marsh shrub to 40.8 g N m⁻² year⁻¹ above- and belowground for the high marsh rush illustrating the importance of incorporating species-specific dynamics into ecosystem N budgets.  相似文献   

The coastal sustainability standard: A management systems approach to ICZM     

Anthony Gallagher 《Ocean & Coastal Management》2010,53(7):336-349

This paper presents a systems-based appraisal methodology that has been designed specifically to consider the effectiveness of Integrated Coastal Zone Management (ICZM) initiatives. Since ICZM is defined in terms of achieving sustainable development, any such initiative must therefore be capable of meeting the multiple and often conflicting objectives inherent in this ubiquitous concept. The methodology outlined here is designed to critically review ICZM in order to pinpoint areas of management weakness and determine the likely ‘success’ of the process. It represents an example of a management system, incorporates both qualitative and quantitative information, and is proposed as a ‘Coastal Sustainability Standard’ (CoSS). Initial field testing of the methodology has proved successful and shown that the approach holds some efficacy as a means of assessment.  相似文献   

An observational study of a magneto-acoustic wave in the solar corona     

D. R. Williams  M. Mathioudakis  P. T. Gallagher  K. J. H. Phillips  R. T. J. MAteer  F. P. Keenan  P. Rudawy  A. C. Katsiyannis 《Monthly notices of the Royal Astronomical Society》2002,336(3):747-752

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A STUDY ON CELLULAR AUTOMATA BASED ON RELATIONAL DATABASES AND SPATIO-TEMPORAL SIMULATIONS OF CULTURE DIFFUSION   总被引：2，自引：0，他引：2  

MICHAELGallagher NIUHui-en LUOPing DUQing-yun HESu-fang LISen 《中国地理科学(英文版)》2002,12(4):359-365

This paper presents a development of the extended Cellular Automata (CA), based on relational databases(RDB), to model dynamic interactions among spatial objects. The integration of Geographical Information System (GIS)and CA has the great advantage of simulating geographical processes. But standard CA has some restrictions in cellularshape and neighbourheod and neighbour rules, which restrict the CA‘s ability to simulate complex, real world environ-ments. This paper discusses a cell‘‘s spatial relation based on the spatial object‘s geometrical and non-geometrical characteris-tics, and extends the cell‘‘ s neighbour definition, and considers that the cell‘ s neighbour lies in the forms of not only spa-tial adjacency but also attribute correlation. This paper then puts forward that spatial relations between two different ceilscan be divided into three types, including spatial adjacency, neighbourheod and complicated separation. Based on tradition-al ideas, it is impossible to settle CA‘‘s restrictions completely. RDB-based CA is an academic experiment, in whichsome fields are designed to describe the essential information needed to define and select a cell‘‘s neighbour. The cultureinnovation diffusion system has multiple forms of space diffusion and inherited characteristics that the RDB-based CA iscapable of simulating more effectively. Finally this paper details a successful case study on the diffusion of fashion weartrends. Compared to the original CA, the RDB-based CA is a more natural and efficient representation of human knowl-edge over space, and is an effective tool in simulating complex systems that have multiple forms of spatial diffusion.  相似文献   

Plasma diagnostics of active-region evolution and implications for coronal heating     

R. O. Milligan  P. T. Gallagher  M. Mathioudakis  F. P. Keenan  D. S. Bloomfield 《Monthly notices of the Royal Astronomical Society》2005,363(1):259-267

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