The ROSAT International X-ray/Optical Survey (RIXOS): source catalogue     

K. O. Mason  F. J. Carrera  G. Hasinger  H. Andernach  A. Aragon-Salamanca  X. Barcons  R. Bower  W. N. Brandt  G. Branduardi-Raymont  J. Burgos-Martín  F. Cabrera-Guerra  R. Carballo  F. Castander  R. S. Ellis  J. I. González-Serrano  E. Martínez-González  J. M. Martín-Mirones  R. G. McMahon  J. P. D. Mittaz  K. L. Nicholson  M. J. Page  I. Pérez-Fournon  E. M. Puchnarewicz  E. Romero-Colmenero  A. D. Schwope  B. Vila  M. G. Watson  D. Wonnacott 《Monthly notices of the Royal Astronomical Society》2000,311(3):456-484

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The ROSAT–ESO Flux-Limited X-ray (REFLEX) galaxy cluster survey – II. The spatial correlation function     

C. A. Collins  L. Guzzo  H. Böhringer  P. Schuecker  G. Chincarini  R. Cruddace  S. De Grandi  H. T. MacGillivray  D. M. Neumann  S. Schindler  P. Shaver  W. Voges 《Monthly notices of the Royal Astronomical Society》2000,319(3):939-948

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Superlarge-scale structure in the Durham/UKST Galaxy Redshift Survey     

Andrei G. Doroshkevich  Richard Fong  Henry J. McCracken  rew Ratcliffe  Tom Shanks  Victor I. Turchaninov 《Monthly notices of the Royal Astronomical Society》2000,315(4):767-777

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The APM Survey for cool carbon stars in the Galactic halo – II. The search for dwarf carbon stars     

E. J. Totten  M. J. Irwin  P. A. Whitelock 《Monthly notices of the Royal Astronomical Society》2000,314(3):630-640

We present proper-motion measurements for carbon stars found during the APM Survey for Cool Carbon Stars in the Galactic halo as reported in an earlier paper by Totten & Irwin. Measurements are obtained using a combination of POSSI, POSSII and UKST survey plates supplemented where necessary by CCD frames taken at the Isaac Newton Telescope. We find no significant proper motion for any of the new APM colour-selected carbon stars and so conclude that there are no dwarf carbon stars present within this sample. We also present proper-motion measurements for three previously known dwarf carbon stars and demonstrate that these measurements agree favourably with those previously quoted in the literature, verifying our method of determining proper motions. Results from a complimentary program of JHK photometry obtained at the South African Astronomical Observatory are also presented. Dwarf carbon stars are believed to have anomalous near-infrared colours, and this feature is used for further investigation of the nature of the APM carbon stars. Our results support the use of JHK photometry as a dwarf/giant discriminator and also reinforce the conclusion that none of the new APM-selected carbon stars is a dwarf. Finally, proper-motion measurements combined with extant JHK photometry are presented for a sample of previously known halo carbon stars, suggesting that one of these stars, CLS29, is likely to be a previously unrecognized dwarf carbon star.  相似文献   

Fish assemblage structure on sandy beaches with different anthropogenic influences and proximity of spawning grounds          下载免费PDF全文

Hamilton H Pereira  Leonardo M Neves  Marcus R da Costa  Francisco G Araújo 《Marine Ecology》2015,36(1):16-27

Fish assemblages in an insular (preserved) and a continental (disturbed) sandy beach were compared to assess any changes that could be attributed to anthropogenic influences and/or the proximity of the fish spawning grounds. We expected that the closer geographical position to the spawning grounds and the small amount of anthropogenic disturbance on the insular beach would be likely to provide more suitable conditions for early fish development compared with the continental beach. A total of 192 samples (96 in each beach) were taken, yielding 68 fish species, mostly young‐of‐the‐year. Fish assemblage structure differed significantly between the two beaches. Moreover, the insular beach had higher number of species, number of individuals and biomass compared with the continental beach. The commercially important Clupeiformes Harengula clupeola, Anchoa tricolor and Anchoa januaria, Perciformes Micropogonias furnieri and Mugiliformes Mugil liza were typical species on the insular beach, partitioning the seasonal use of the beach. On the other hand, a few abundant non‐commercial species, mainly the Atheriniformes Atherinella brasiliensis and the Perciformes Eucinostomus argenteus and Diapterus rhombeus, occurred all year round at the continental beach. The high fish richness and abundance and the more conspicuous species turnover across seasons on the insular beach are probable indications of more complex and dynamic organization of the communities favored by better geographical position and less anthropogenic disturbance in the area.  相似文献   

渔业资源调查采样设计优化研究进展   总被引：3，自引：0，他引：3  

唐政  单秀娟  金显仕 《海洋科学》2019,43(4):88-97

渔业资源调查是指利用一定的采样设计,对渔业种群进行空间布点采样,以获取研究区域内鱼类时空分布以及生物学和生态学信息。但是大量的研究表明,不同的鱼类分布适合不同的采样设计,需要根据鱼类的分布特点和调查目标(种群丰度等)优化采样设计,保证数据的准确性和精度。近年来,相关的研究有很多,涉及不同采样设计的比较和应用以及影响数据质量因素的探究。作者着重介绍了定点采样、传统方法、适应性方法和基于地理统计学方法,叙述了计算机模拟及重采样技术在采样设计优化中的应用以及相对偏差、相对估计误差、设计效果和变异系数等评价采样设计性能的指标,同时对采样设计中需要注意的问题进行介绍,最后进行了总结并对未来的研究工作进行展望。  相似文献   

Assessment and integration of conventional,RTK-GPS and image-derived beach survey methods for daily to decadal coastal monitoring   总被引：1，自引：0，他引：1  

Mitchell D. Harley  Ian L. Turner  Andrew D. Short  Roshanka Ranasinghe 《Coastal Engineering》2011

Coastal monitoring across a broad range of time-scales was recognized in the latest report by the Intergovernmental Panel on Climate Change as key to better understanding the likely impacts of climate change at the coast. A unique and historic coastal monitoring program undertaken at the Collaroy–Narrabeen embayment in south-eastern Australia comprises: 1) 30 years of monthly conventional (Emery method) surveys of five cross-shore profile lines; 2) three years of monthly three-dimensional surveys of the entire embayment using RTK-GPS mounted to an all-terrain vehicle (ATV); and 3) four years of hourly shoreline measurements using coastal imaging technology (ARGUS). This study evaluates the strengths and limitations of conventional, RTK-GPS and image-derived surveys for coastal monitoring at daily to decadal coastal time-scales. High-accuracy RTK-GPS was used to first assess the accuracy of the conventional and image-derived survey methods. The magnitude of daily to decadal coastal variability was then characterized by calculating the temporal semivariogram of the integrated survey dataset. With both measurement errors and the degree of beach variability quantified, the corresponding signal-to-noise ratios (SNR) of each survey method at different time-scales were determined. The value of the simple and cost-effective Emery method was verified by this analysis, with measurement error significantly smaller than the degree of overall beach variability (SNR = 8.4). The accuracy, speed and efficiency of ATV-mounted RTK-GPS meanwhile make it suitable for three-dimensional beach surveys. Image-derived surveys were found to be an effective means of remotely measuring the considerable degree of beach variability identified at time-scales of less than one month. These measurements however become indistinguishable from survey noise (i.e. SNR ≤ 1) when considering typical weekly (or smaller) variations at large distances from the cameras.  相似文献   

Erratum: Large-amplitude variables near the Galactic Centre     

I. S. Glass  S. Matsumoto  B. S. Carter  K. Sekiguchi 《Monthly notices of the Royal Astronomical Society》2002,336(4):1390-1390

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The distance to Supernova 1998aq in NGC 3982     

Peter B. Stetson †  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2001,328(1):L1-L4

We use the preliminary results of a new survey of radio sources made using the Ryle Telescope at 15.2 GHz, to estimate the impact of foreground sources on cm-wave cosmic microwave background (CMB) images. This is the highest frequency survey that is relevant to the issue of radio source contamination in CMB experiments. The differential source count of the 66 sources found in 63 deg² is     , from ≈20 to ≈500 mJy. Extrapolating this to 34 GHz (where many cm-wave CMB experiments operate) gives an estimated temperature contribution of sources     in a CMB image, with a beam corresponding to multipole     . A means of source subtraction is evidently necessary, otherwise the signal-to-noise ratio in CMB images will be limited to 4 or 5, becoming worse at higher resolution. We compare the population of sources observed in this new survey to that predicted by extrapolation from lower frequency surveys, finding that source flux densities, and indeed the existence of many sources, cannot be determined by extrapolation.  相似文献   

Power spectrum analysis of the ESO Slice Project galaxy redshift survey     

E. Carretti  C. Bertoni  A. Messina  E. Zucca  L. Guzzo 《Monthly notices of the Royal Astronomical Society》2001,324(4):1029-1040

We measure the power spectrum of the galaxy distribution in the ESO Slice Project (ESP) galaxy redshift survey. We develop a technique to describe the survey window function analytically, and then deconvolve it from the measured power spectrum using a variant of the Lucy method. We test the whole deconvolution procedure on ESP mock catalogues drawn from large N -body simulations, and find that it is reliable for recovering the correct amplitude and shape of P ( k ) at k >0.065  h  Mpc⁻¹. In general, the technique is applicable to any survey composed of a collection of circular fields with an arbitrary pattern on the sky, as typical of surveys based on fibre spectrographs. The estimated power spectrum has a well-defined power-law shape k ⁿ with n ≃−2.2 for k ≥0.2  h  Mpc⁻¹, and a smooth bend to a flatter shape ( n ≃−1.6) for smaller k . The smallest wavenumber where a meaningful reconstruction can be performed ( k ∼0.06  h  Mpc⁻¹) does not allow us to explore the range of scales where other power spectra seem to show a flattening and hint at a turnover. We also find, by a direct comparison of the Fourier transforms, that the estimate of the two-point correlation function ξ ( s ) is much less sensitive to the effect of a problematic window function, such as that of the ESP, than the power spectrum. Comparison with other surveys shows an excellent agreement with estimates from blue-selected surveys. In particular, the ESP power spectrum is virtually indistinguishable from that of the Durham–UKST survey over the common range of k , an indirect confirmation of the quality of the deconvolution technique applied.  相似文献