A new method of measuring the cluster peculiar velocity power spectrum     

Pengjie Zhang  Hume A. Feldman  Roman Juszkiewicz  Albert Stebbins 《Monthly notices of the Royal Astronomical Society》2008,388(2):884-888

We propose to use spatial correlations of the kinetic Sunyaev–Zeldovich (KSZ) flux as an estimator of the peculiar velocity power spectrum. In contrast with conventional techniques, our new method does not require measurements of the thermal SZ signal or the X-ray temperature. Moreover, this method has the special advantage that the expected systematic errors are always subdominant to statistical errors on all scales and redshifts of interest. We show that future large sky coverage KSZ surveys may allow a peculiar velocity power spectrum estimates of an accuracy reaching ∼10 per cent.  相似文献   

A low cosmic microwave background variance in the Wilkinson Microwave Anisotropy Probe data     

C. Monteserín  R. B. Barreiro  P. Vielva  E. Martínez-González  M. P. Hobson  A. N. Lasenby 《Monthly notices of the Royal Astronomical Society》2008,387(1):209-219

We have estimated the cosmic microwave background (CMB) variance from the three-year Wilkinson Microwave Anisotropy Probe ( WMAP ) data, finding a value which is significantly lower than the one expected from Gaussian simulations using the WMAP best-fitting cosmological model, at a significance level of 98.7 per cent. This result is even more prominent if we consider only the North ecliptic hemisphere (99.8 per cent). Different analyses have been performed in order to identify a possible origin for this anomaly. In particular, we have studied the behaviour of single-radiometer and single-year data as well as the effect of residual foregrounds and 1/f noise, finding that none of these possibilities can explain the low value of the variance. We have also tested the effect of varying the cosmological parameters, finding that the estimated CMB variance tends to favour higher values of n _s than the one of the WMAP best-fitting model. In addition, we have also tested the consistency between the estimated CMB variance and the actual measured CMB power spectrum of the WMAP data, finding a strong discrepancy. A possible interpretation of this result could be a deviation from Gaussianity and/or isotropy of the CMB.  相似文献   

Determining the motion of the Solar system relative to the cosmic microwave background using Type Ia supernovae     

Christopher Gordon  Kate Land  An&#;e Slosar 《Monthly notices of the Royal Astronomical Society》2008,387(1):371-376

We estimate the Solar system motion relative to the cosmic microwave background using Type Ia supernovae (SNe) measurements. We take into account the correlations in the error bars of the SNe measurements arising from correlated peculiar velocities. Without accounting for correlations in the peculiar velocities, the SNe data we use appear to detect the peculiar velocity of the Solar system at about the 3.5σ level. However, when the correlations are correctly accounted for, the SNe data only detect the Solar system peculiar velocity at about the 2.5σ level. We forecast that the Solar system peculiar velocity will be detected at the 9σ level by GAIA and the 11σ level by the Large Synoptic Survey Telescope. For these surveys, we find the correlations are much less important as most of the signal comes from higher redshifts where the number density of SNe is insufficient for the correlations to be important.  相似文献   

Mixed three-point correlation functions of the non-linear integrated Sachs–Wolfe effect and their detectability     

B. M. Schäfer 《Monthly notices of the Royal Astronomical Society》2008,388(3):1394-1402

In this paper, I investigate the family of mixed three-point correlation functions  〈τ ^q γ^{3− q} 〉, q = 0, 1, 2  , between the integrated Sachs–Wolfe (iSW) temperature perturbation τ and the galaxy overdensity γ as a tool for detecting the gravitational interaction of cosmic microwave background (CMB) photons with the potentials of non-linearly evolving cosmological structures. Both the iSW-effect and the galaxy overdensity are derived in hyperextended perturbation theory to second order and I emphasize the different parameter sensitivities of the linear and non-linear iSW-effect. I examine the configuration dependence of the relevant bispectra, quantify their sensitivities and discuss their degeneracies with respect to the cosmological parameters  Ω_m, σ₈, h   and the dark energy equation of state parameter w . I give detection significances for combining Planck CMB data and galaxy sample of a survey like Dark UNiverse Explorer (DUNE) by using a quadratic approximation for the likelihood with Λ cold dark matter (ΛCDM) as the fiducial cosmology: the combination of Planck with DUNE should be able to reach a cumulative signal-to-noise ratio of ≃0.6 for the bispectrum  〈τγ²〉  up to ℓ= 2000, which is too weak to be detected. The most important noise source is the primary CMB fluctuations as the Poisson noise in the galaxy number density is almost negligible for a survey like DUNE.  相似文献   

A new method for determining the sensitivity of X-ray imaging observations and the X-ray number counts     

A. Georgakakis †  K. Nandra  E. S. Laird  J. Aird  M. Trichas 《Monthly notices of the Royal Astronomical Society》2008,388(3):1205-1213

We present a new method for determining the sensitivity of X-ray imaging observations, which correctly accounts for the observational biases that affect the probability of detecting a source of a given X-ray flux, without the need to perform a large number of time-consuming simulations. We use this new technique to estimate the X-ray source counts in different spectral bands (0.5–2, 0.5–10, 2–10 and 5–10 keV) by combining deep pencil-beam and shallow wide-area Chandra observations. The sample has a total of 6295 unique sources over an area of  11.8 deg²  and is the largest used to date to determine the X-ray number counts. We determine, for the first time, the break flux in the 5–10 keV band, in the case of a double power-law source count distribution. We also find an upturn in the 0.5–2 keV counts at fluxes below about  6 × 10⁻¹⁷ erg s⁻¹ cm⁻²  . We show that this can be explained by the emergence of normal star-forming galaxies which dominate the X-ray population at faint fluxes. The fraction of the diffuse X-ray background resolved into point sources at different spectral bands is also estimated. It is argued that a single population of Compton thick active galactic nuclei (AGN) cannot be responsible for the entire unresolved X-ray background in the energy range 2–10 keV.  相似文献   

北京地区大气PM10和SO2的背景浓度分析   总被引：16，自引：1，他引：15  

蔡旭晖  张睿  宋宇  谢绍东 《气候与环境研究》2004,9(3):445-453

用 2 0 0 0年 1、 4、 7、 1 0月北京地区 5个测站的逐时环境监测资料 ,同期 2 0个测点的逐时气象观测数据 ,结合风场诊断和随机游走扩散模拟方法 ,分析北京城区污染物的输送扩散作用对郊外清洁对照点 (定陵站 )浓度监测结果的影响 ,并初步推断这一地区大气可吸入颗粒物 (PM1 0 )和二氧化硫 (SO2 )的背景浓度。结果表明 ,清洁对照点定陵站受北京城区大气污染物的影响显著。去除这种影响并经进一步的概率分析 ,获得本地区SO2 的背景浓度估计值在冬季 ( 1月 )约为 0 0 4 4mgm- 3 以下 ,其他各季约为 0 0 0 8mgm- 3;PM1 0在冬春夏季 ( 1、 4、 7月 )的背景浓度估计值约为 0 0 3～ 0 0 4mgm- 3,秋季( 1 0月 )约为 0 0 1～ 0 0 2mgm- 3。  相似文献   

燕山运动与东亚构造体制的转变   总被引：92，自引：7，他引：85  

赵越  徐刚  张拴宏  杨振宇  张岳桥  胡健民 《地学前缘》2004,11(3):319-328

构造体制转变的本质是动力学体系的转变。东亚构造体制的转变是从一个汇聚碰撞的动力学体系转变为一个活动大陆边缘的动力学体系。其核心问题是古太平洋板块开始向新生的亚洲大陆下俯冲。在这一独特的动力学体系转变过程中 ,产生了陆缘俯冲消减增生杂岩带 ,火山弧和相关的表壳变形等一系列标志。文中强调以自然的、显著的、易于识别的标志———火山弧的出现代表东亚构造域动力学体系的转变 ;指出翁文灏命名的燕山运动A幕———髫髻山组火山岩下的不整合 ( ( 16 0± 5 )Ma前 )和B幕———张家口组火山岩下的不整合 ( ( 13 5± 1)Ma前 )代表这一转变。也就是说 ,燕山运动是东亚构造体制转变的产物 ,其出现有着深刻的地球动力学背景  相似文献   

生态地质条件评估的方法、原理和标准     

V.T.TROFIMOV 《地学前缘》2004,11(2):533-542

文中确定了“生态地质条件”及“生态地质条件的现状”等术语的意义 ;阐述了用于评估生态地质条件的方法、原理以及标准和指标的分类 ;论述了地球动力学和地球物理学的标准和指标  相似文献   

斑岩Cu-Mo-Au矿床:新认识与新进展   总被引：59，自引：0，他引：59  

侯增谦 《地学前缘》2004,11(1):131-144

斑岩型矿床作为一种最重要的铜钼和铜金矿床类型一直得到人们的普遍重视 ,近些年来又取得了重要研究进展 ,主要体现在 5个方面 :①岛弧和陆缘弧是斑岩型矿床产出的重要环境 ,但大陆碰撞造山带也具有产出斑岩型矿床的巨大潜力。按矿床产出的构造环境 ,可以分为弧造山型斑岩矿床和碰撞造山型斑岩矿床 ;②弧造山型含矿斑岩主要为钙碱性和高钾钙碱性 ,而碰撞造山型含矿斑岩则主要为高钾钙碱性和橄榄安粗质 (shoshonitic)。两种环境的含矿斑岩多具有埃达克岩 (adakite)岩浆亲合性 ,但前者主要来源于俯冲的大洋板片 ,后者主要来源于碰撞加厚的下地壳。大洋板片的部分熔融缘于俯冲角度的平缓化 ,而加厚下地壳的熔融起因于俯冲大陆板片的断离 (slabbreakoff) ;③在弧造山环境 ,大洋俯冲板片的膝折 (kink)或撕裂 (slabtear)不仅导致俯冲角度变缓 ,而且引起弧地壳耦合变形 ,产生切弧断裂 ,控制斑岩铜系统的时空分布。俯冲板片撕裂引发软流圈上涌 ,诱发大洋板片熔融 ,产生含矿岩浆 ;④在碰撞造山环境 ,大陆俯冲板片的裂离导致软流圈上涌 ,向下地壳注入新生物质 ,并诱发下地壳物质熔融 ,产生含矿岩浆。碰撞后地壳伸展形成横切碰撞带的正断层系统 ,为斑岩侵位提供运移通道 ,并导致岩浆流体大量分凝和铜钼金淀积。不论  相似文献   

中国红层的分布及地质环境特征   总被引：47，自引：3，他引：44  

程强寇小兵  黄绍槟周永江 《工程地质学报》2004,12(1):34-40

根据我国红层的分布特征及形成背景 ,将我国红层划分为西南地区红层、西北地区红层、中南、东南地区红层和其他地区 (西藏及华北的部分地区 )红层。重点研究了以川滇红层为代表的西南地区红层和以甘肃红层为代表的西北地区红层 ,研究了各个区域红层的地质构造特征、地形地貌特征、气候环境特征等工程地质环境特征 ,根据工程地质环境特征 ,将研究区域的红层划分为四川盆地红层、西昌滇中红层、滇西红层和甘肃红层.  相似文献