Relativistic corrections to the Kompaneets equation     

《Astroparticle Physics》2015

We study the Sunyaev–Zeldovich effect for clusters of galaxies. We explore the relativistic corrections to the Kompaneets equation in terms of two different expansion approximation schemes, namely, the Fokker–Planck expansion approximation and delta function expansion approximation. We show that two expansion approximation formalisms are equivalent under the Thomson approximation, which is extremely good approximation for the CMB photon energies. This will clarify the situation for existing theoretical methods to analyse observation data.  相似文献   

主动微波遥感黄河上游玛曲地区夏季土壤水分   总被引：6，自引：1，他引：5       下载免费PDF全文

田辉  文军  史小康  王欣  刘蓉  张静辉  吕少宁 《水科学进展》2011,22(1):59-66

利用ENVISAT-1/ASAR的VV极化主动微波资料,基于裸土表层微波后向散射GOM物理模型,并利用"水-云"模型处理植被层对土壤表层微波后向散射的影响,遥感估算了夏季黄河上游玛曲地区土壤水分空间分布.通过地面观测网的同步观测资料验证,卫星遥感的土壤体积水分含量和地面测值间的均方根误差RMSE<0.02 m3/m3,...  相似文献   

On the structure and propagation of internal solitary waves generated at the Mascarene Plateau in the Indian Ocean     

J.C.B. da Silva  A.L. NewJ.M. Magalhaes 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(3):229-240

Analysis of a comprehensive dataset of Synthetic Aperture Radar (SAR) images acquired over the sea area around the Mascarene Plateau in the western Indian Ocean reveals, for the first time, the full two-dimensional spatial structure of internal solitary waves in this region of the ocean. The satellite SAR images show that powerful internal waves radiate both to the west and east from a central sill near 12.5°S, 61°E between the Saya de Malha and Nazareth Banks. To first order, the waves appear in tidally generated packets on both sides of the sill, and those on the western side have crest lengths in excess of 350 km, amongst the longest yet recorded anywhere in the world's oceans. The propagation characteristics of these internal waves are well described by first mode linear waves interacting with background shear taken from the westward-flowing South Equatorial Current (SEC), a large part of which flows through the sill in question. Analysis of the timings and locations of the packets indicates that both the westward- and eastward-traveling waves are generated from the western side of the sill at the predicted time of maximum tidal flow to the west. The linear generation mechanism is therefore proposed as the splitting of a large lee wave that forms on the western side of the sill, in a similar manner to that already identified for the shelf break generation of internal waves in the northern Bay of Biscay. While lee waves should form on either side of the sill in an oscillatory tidal flow, that on the western side would be expected to be much larger than that on the eastern side because of a superposition of the tidal flow and the steady westward flow of SEC. The existence of a large lee wave at the right time in the tidal cycle is then finally confirmed by direct observations. Our study also confirms the existence of second mode internal waves that form on the western side of the sill and travel across the sill towards the east.  相似文献   

A study of the Sunyaev–Zel'dovich increment using archival SCUBA data     

Michael Zemcov &#;  Colin Borys  Mark Halpern  Philip Mauskopf  Douglas Scott 《Monthly notices of the Royal Astronomical Society》2007,376(3):1073-1098

In a search for evidence of the short wavelength increment in the Sunyaev–Zel'dovich (SZ) effect, we have analysed archival galaxy cluster data from the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope, resulting in the most complete pointed survey of clusters at 850 μm to date. SCUBA's 850-μm passband overlaps the peak of the SZ increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3. Maps of each of the clusters have been made and sources have been extracted; as an ancillary product, we generate the most thorough galaxy cluster point source list yet from SCUBA. 17 of these clusters are free of obvious active galactic nuclei (AGN) and have data deep enough to provide interesting measurements of the expected SZ signal. Specialized analysis techniques are employed to extract the SZ effect signal from these SCUBA data, including using SCUBA's short wavelength band as an atmospheric monitor and fitting the long wavelength channel to a model of the spatial distribution of each cluster's SZ effect. By explicitly excising the exact cluster centre from our analysis, we demonstrate that emission from galaxies within the cluster does not contaminate our measurement. The SZ amplitudes from our measurements are consistently higher than the amplitudes inferred from low-frequency measurements of the SZ decrement.  相似文献   

Anomalous SZ contribution to three-year WMAP data     

R. M. Bielby  T. Shanks 《Monthly notices of the Royal Astronomical Society》2007,382(3):1196-1202

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Measuring the primordial power spectrum: principal component analysis of the cosmic microwave background     

Samuel Leach 《Monthly notices of the Royal Astronomical Society》2006,372(2):646-654

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Absolute Parameters of Early-Type Close Binaries in the LMC     

S. Nesslinger  H. Drechsel 《Astrophysics and Space Science》2006,304(1-4):211-214

A project is presented which aims at high-precision determination of absolute parameters of close early-type eclipsing binaries in the LMC. We will use multi-object spectrographs (MOS) to measure RV curves of a large number of program stars selected from the MACHO archive. Spectroscopic mass ratios will be used as input for our light curve analysis code MORO. Application of the Simplex-based algorithm FITSB2 will achieve spectrum disentangling and fitting of NLTE model (TLUSTY) atmospheres, yielding orbital and atmospheric parameters. The method was extensively tested by application to time series of synthetic binary spectra for the expected range of S/N and MOS instrumental resolution. log g and T _eff were reestablished with a precision of better than 5%, radial velocity amplitudes with errors of <3%. An important by-product of our project will be the improvement of the distance modulus of the LMC, a topic which is still being intensely discussed.  相似文献   

1.4-GHz polarimetric observations of the two fields imaged by the DASI experiment     

G. Bernardi  E. Carretti †  R. J. Sault  S. Cortiglioni  S. Poppi 《Monthly notices of the Royal Astronomical Society》2006,370(4):2064-2070

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Lines in the cosmic microwave background spectrum from the epoch of cosmological hydrogen recombination     

J. A. Rubiño-Martín  J. Chluba  R. A. Sunyaev 《Monthly notices of the Royal Astronomical Society》2006,371(4):1939-1952

We compute the spectral distortions of the cosmic microwave background (CMB) arising during the epoch of cosmological hydrogen recombination within the standard cosmological (concordance) model for frequencies in the range 1–3500 GHz. We follow the evolution of the populations of the hydrogen levels including states up to principle quantum number   n = 30  in the redshift range  500 ≤ z ≤ 3500  . All angular momentum substates are treated individually, resulting in a total number of 465 hydrogen levels. The evolution of the matter temperature and the fraction of electrons coming from He  ii are also included. We present a detailed discussion of the distortions arising from the main dipolar transitions, for example Lyman and Balmer series, as well as the emission due to the two-photon decay of the hydrogen 2s level. Furthermore, we investigate the robusteness of the results against changes in the number of shells considered. The resulting spectral distortions have a characteristic oscillatory behaviour, which might allow experimentalists to separate them from other backgrounds. The relative distortion of the spectrum exceeds a value of 10⁻⁷ at wavelengths longer than 21 cm. Our results also show the importance of detailed follow-up of the angular momentum substates, and their effect on the amplitude of the lines. The effect on the residual electron fraction is only moderate, and mainly occurs at low redshifts. The CMB angular power spectrum is changed by less than 1 per cent. Finally, our computations show that if the primordial radiation field is described by a pure blackbody, then there is no significant emission from any hydrogen transition at redshifts greater than   z ∼ 2000  . This is in contrast to some earlier works, where the existence of a 'pre-recombination' peak was claimed.  相似文献   

Detecting Sunyaev–Zel'dovich clusters with Planck– III. Properties of the expected SZ cluster sample     

Björn Malte Schäfer  Matthias Bartelmann 《Monthly notices of the Royal Astronomical Society》2007,377(1):253-268

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