Optical and near-infrared colours as a discriminant of the age and metallicity of stellar populations     

David Carter  Daniel J. B. Smith  Susan M. Percival  Ivan K. Baldry  Christopher A. Collins  Philip A. James  Maurizio Salaris  Chris Simpson  John P. Stott  Bahram Mobasher 《Monthly notices of the Royal Astronomical Society》2009,397(2):695-708

We present a comprehensive analysis of the ability of current stellar population models to reproduce the optical ( ugriz ) and near-infrared ( JHK ) colours of a small sample of well-studied nearby elliptical and S0 galaxies. We find broad agreement between the ages and metallicities derived using different population models, although different models show different systematic deviations from the measured broad-band fluxes. Although it is possible to constrain simple stellar population models to a well-defined area in age–metallicity space, there is a clear degeneracy between these parameters even with such a full range of precise colours. The precision to which age and metallicity can be determined independently, using only broad-band photometry with realistic errors, is  Δ[Fe/H]≃ 0.18  and  Δlog Age ≃ 0.25  . To constrain the populations and therefore the star formation history further, it will be necessary to combine broad-band optical–IR photometry with either spectral line indices, or else photometry at wavelengths outside this range.  相似文献   

西藏恰功铁矿岩浆演化序列及斑岩出溶流体特征   总被引：6，自引：1，他引：5  

谢玉玲  李应栩  Zhaoshan CHANG  David R. COOKE  Chris G. RYAN  Jamie LAIRD  白劲松  刘云飞  李光明  张丽 《地质学报》2009,83(12):1869-1886

冈底斯成矿带是碰撞造山过程形成的最重要的成矿带,恰功矽卡岩铁(铜)矿床即位于冈底斯成矿带中部.本文在详细的野外地质填图和室内研究基础上确定了恰功铁矿与成矿有关的斑岩体为二长花岗斑岩,锆石的U-Pb定年结果为68.8±2.2 Ma,明显早于冈底斯东部与后碰撞伸展有关的斑岩型矿床和主碰撞期形成的矽卡岩型矿床,其应代表了冈底斯一次尚未被充分认识到的成矿事件.通过对成矿斑岩的岩石学、岩石化学、岩浆出溶流体的包裹体岩相学、显微测温分析及包裹体成分的LRM、LA-ICP-MS和PIXE分析,本文探讨了与该矽卡岩矿床有关的斑岩的岩浆起源、斑岩侵位机制及出溶流体特征.结果表明,成矿斑岩为矿区最早的侵入岩单元,具有壳幔源混源特征,其常量元素组成与冈底斯东部斑岩铜矿带的埃达克质岩相近,但稀土和微量元素组成与东部斑岩明显不同,为地幔物质上涌并诱发角闪岩相下地壳熔融的产物,岩体侵位深度大(>7 km)、剥蚀程度高.早期岩浆出溶的流体为高温、高压、高盐度流体,其中富含Fe、Pb、Zn、Cu等成矿金属,与世界其他斑岩铜矿床相比,相对富铁、铅而贫铜.流体的沸腾作用发生于钾硅化阶段,形成了一套富气、高盐、高固相和气液包裹体组合,不同于早期出溶流体的包裹体组合.从岩浆起源和出溶流体性质可以看出,该斑岩具有形成与斑岩有关的铁铅多金属矿床的成矿潜力,但从该矿区地表出露的蚀变和包裹体测压结果可以看出,该斑岩体目前剥蚀深度较大,对斑岩型矿床保存不利,对该斑岩体及与成矿关系的认识对理解该区内的矿床成因和指导区域找矿具有重要的指示意义.  相似文献   

The ‘view from nowhere’? Spatial politics and cultural significance of high-resolution satellite imagery     

Martin Dodge  Chris Perkins   《Geoforum》2009,40(4):497-501

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Complex statistics in Hamiltonian barred galaxy models     

Tassos Bountis  Thanos Manos  Chris Antonopoulos 《Celestial Mechanics and Dynamical Astronomy》2012,113(1):63-80

We use probability density functions (pdfs) of sums of orbit coordinates, over time intervals of the order of one Hubble time, to distinguish weakly from strongly chaotic orbits in a barred galaxy model. We find that, in the weakly chaotic case, quasi-stationary states arise, whose pdfs are well approximated by q-Gaussian functions (with 1 <?q < 3), while strong chaos is identified by pdfs which quickly tend to Gaussians (q =?1). Typical examples of weakly chaotic orbits are those that ??stick?? to islands of ordered motion. Their presence in rotating galaxy models has been investigated thoroughly in recent years due to their ability to support galaxy structures for relatively long time scales. In this paper, we demonstrate, on specific orbits of 2 and 3 degree of freedom barred galaxy models, that the proposed statistical approach can distinguish weakly from strongly chaotic motion accurately and efficiently, especially in cases where Lyapunov exponents and other local dynamic indicators appear to be inconclusive.  相似文献   

A longer-term perspective on soil moisture,groundwater and stream flow response to the 2018 drought in an experimental catchment in the Scottish Highlands     

Chris Soulsby  Bernhard Scheliga  Aaron Neill  Jean-Christophe Comte  Doerthe Tetzlaff 《水文研究》2021,35(6):e14206

The drought of summer 2018, which affected much of Northern Europe, resulted in low river flows, biodiversity loss and threats to water supplies. In some regions, like the Scottish Highlands, the summer drought followed two consecutive, anomalously dry, winter periods. Here, we examine how the drought, and its antecedent conditions, affected soil moisture, groundwater storage, and low flows in the Bruntland Burn; a sub-catchment of the Girnock Burn long-term observatory in the Scottish Cairngorm Mountains. Fifty years of rainfall-runoff observations and long-term modelling studies in the Girnock provided unique contextualisation of this extreme event in relation to more usual summer storage dynamics. Whilst summer precipitation in 2018 was only 63% of the long-term mean, soil moisture storage across much of the catchment were less than half of their summer average and seasonal groundwater levels were 0.5 m lower than normal. Hydrometric and isotopic observations showed that ~100 mm of river flows during the summer (May-Sept) were sustained almost entirely by groundwater drainage, representing ~30% of evapotranspiration that occurred over the same period. A key reason that the summer drought was so severe was because the preceding two winters were also dry and failed to adequately replenish catchment soil moisture and groundwater stores. As a result, the drought had the biggest catchment storage deficits for over a decade, and likely since 1975–1976. Despite this, recovery was rapid in autumn/winter 2018, with soil and groundwater stores returning to normal winter values, along with stream flows. The study emphasizes how long-term data from experimental sites are key to understanding the non-linear flux-storage interactions in catchments and the “memory effects” that govern the evolution of, and recovery from, droughts. This is invaluable both in terms of (a) giving insights into hydrological behaviours that will become more common water resource management problems in the future under climate change and (b) providing extreme data to challenge hydrological models.  相似文献   

Modelling ecohydrological feedbacks in forest and grassland plots under a prolonged drought anomaly in Central Europe 2018–2020     

Lukas Kleine  Doerthe Tetzlaff  Aaron Smith  Maren Dubbert  Chris Soulsby 《水文研究》2021,35(8):e14325

Recent studies have highlighted the importance of understanding ecohydrological drought feedbacks to secure water resources under a changing climate and increasing anthropogenic impacts. In this study, we monitored and modelled feedbacks in the soil–plant-atmosphere continuum to the European drought summer 2018 and the following 2 years. The physically based, isotope-aided model EcH₂O-iso was applied to generic vegetation plots (forest and grassland) in the lowland, groundwater-dominated research catchment Demnitzer Millcreek (NE Germany; 66 km²). We included, inter alia, soil water isotope data in the model calibration and quantified changing “blue” (groundwater recharge) and “green” (evapotranspiration) water fluxes and ages under each land use as the drought progressed. Novel plant xylem isotope data were excluded from calibration but were compared with simulated root uptake signatures in model validation. Results indicated inter-site differences in the dynamics of soil water storage and fluxes with contrasting water age both during the drought and the subsequent 2 years. Forest vegetation consistently showed a greater moisture stress, more rapid recovery and higher variability in root water uptake depths from a generally younger soil water storage. In contrast, the grassland site, which had more water-retentive soils, showed higher and older soil water storage and groundwater recharge fluxes. The damped storage and flux dynamics under grassland led to a slower return to younger water ages at depth. Such evidence-based and quantitative differences in ecohydrological feedbacks to drought stress in contrasting soil-vegetation units provide important insights into Critical Zone water cycling. This can help inform future progress in the monitoring, modelling and development of climate mitigation strategies in drought-sensitive lowlands.  相似文献   

Using a fluvial archive to place extreme flood sediment (dis)connectivity dynamics in context of a longer-term record     

Kirstie Fryirs  Chris Thompson  Damian Gore 《国际泥沙研究》2022,37(4):447-456

The aim of this study was to establish the source and provenance of sediments deposited in a large floodplain sink during extreme floods in the Lockyer Creek catchment, Australia, in 2011 and 2013. We place the sediment source patterns in context of the longer-term record to determine whether coarse-grained sediment sources (i.e., very fine sand to very coarse sand) and the spatio-temporal pattern of (dis)connectivity have changed over time. We do this by matching the geochemical properties and age structure of a sediment profile located in a downstream floodplain sink to the elemental composition of source sediments. One hundred and fifty-seven sediment samples from 20 sites across the catchment are analysed using X-ray fluorescence (XRF) spectrometry to compare the elemental ratio composition of the downstream floodplain sink to its source materials. We use Optically Stimulated Luminescence (OSL) dating to determine the age structure of the sediments in the floodplain sink. The northern tributaries and parts of the Lockyer River trunk stream are the primary sources of coarse sediment. These areas are connected (coupled) to the lower trunk stream and floodplain sediment sink. Southern tributaries are largely disconnected (decoupled) and supply little sediment to the floodplain sediment sink. This pattern of sediment source contribution has remained similar over the last 6.8 ka at least. Sediment sources as observed in the 2011 flood have predominated over the mid-late Holocene whilst those in the 2013 flood are rare.  相似文献   

An analytical model of surface mass densities of cold dark matter haloes – with an application to MACHO microlensing optical depths     

Janne Holopainen  Erik Zackrisson  Alexander Knebe  Pasi Nurmi  Pekka Heinämäki  Chris Flynn  Stuart Gill  Teresa Riehm 《Monthly notices of the Royal Astronomical Society》2008,383(2):720-728

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Halo-model signatures from 380 000 Sloan Digital Sky Survey luminous red galaxies with photometric redshifts     

Chris Blake  Adrian Collister  Ofer Lahav 《Monthly notices of the Royal Astronomical Society》2008,385(3):1257-1269

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Exploring the infrared/radio correlation at high redshift     

Edo Ibar  Michele Cirasuolo  Rob Ivison  Philip Best  Ian Smail  y Biggs  Chris Simpson  Jim Dunlop  Omar Almaini  Ross McLure  Sebastien Foucaud  Steve Rawlings 《Monthly notices of the Royal Astronomical Society》2008,386(2):953-962

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