Bivariate galaxy luminosity functions in the Sloan Digital Sky Survey     

N. M. Ball  J. Loveday  R. J. Brunner  I. K. Baldry  J. Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,373(2):845-868

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A SCUBA scan-map of the Hubble Deep Field: measuring the bright end of the submillimetre source counts     

ColinBorys  Scott C.Chapman  MarkHalpern  DouglasScott 《Monthly notices of the Royal Astronomical Society》2002,330(3):L63-L67

Using the 850-μm SCUBA camera on the JCMT and a scanning technique different from other sub-mm surveys, we have obtained a 125 arcmin² map centred on the Hubble Deep Field . The 1 σ sensitivity to point sources is roughly 3 mJy and thus our map probes the brighter end of the sub-mm source counts. We find six sources with a flux greater than about 12 mJy (>4 σ ) and, after a careful accounting of incompleteness and flux bias, estimate the integrated density of bright sources     (68 per cent confidence bounds).  相似文献   

宽带频谱序列干扰信号识别与统计方法   总被引：1，自引：0，他引：1  

王利云  刘奇  陈卯蒸  刘晔  王玥  朱春花  王洋 《天文学报》2019,60(5):34-43

随着科学技术的不断进步,射电天文台站趋于自动化,各类电子设备的广泛使用使得射电天文台站的电磁环境变得尤为复杂,如何有效识别和统计复杂频谱中的干扰信号是当前射电天文台站亟需解决的问题,故提出一种宽带频谱序列干扰信号识别与统计方法.首先,对每组宽带频谱进行信噪分离、识别频谱中的干扰信号;然后,对第1组宽带频谱信号识别结果及信号特征建立模板库,后续每组频谱的信号识别结果与模板库中对应频率的信号进行相似性分析,根据相似性分析结果,统计信号次数,更新模板库;实现宽带频谱序列干扰信号的识别与统计.针对QTT (QiTai Radio Telescope)台站实测频谱,运用该方法进行干扰信号识别与统计,能够有效识别并标记频谱中的干扰信号,并统计干扰信号随时间、方向的变化趋势.  相似文献   

The DEEP2 Galaxy Redshift Survey: the relationship between galaxy properties and environment at z∼ 1     

Michael C. Cooper  Jeffrey A. Newman †  Darren J. Croton  Benjamin J. Weiner  Christopher N. A. Willmer  Brian F. Gerke  Darren S. Madgwick †  S. M. Faber  Marc Davis  Alison L. Coil †  Douglas P. Finkbeiner  Puragra Guhathakurta  David C. Koo 《Monthly notices of the Royal Astronomical Society》2006,370(1):198-212

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Testing homogeneity on large scales in the Sloan Digital Sky Survey Data Release One     

Jaswant Yadav  Somnath Bharadwaj  Biswajit Pandey  T. R. Seshadri 《Monthly notices of the Royal Astronomical Society》2005,364(2):601-606

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Statistical analysis of galaxy surveys – II. The three-point galaxy correlation function measured from the 2dFGRS     

E. Gaztañaga  P. Norberg  C. M. Baugh  D. J. Croton 《Monthly notices of the Royal Astronomical Society》2005,364(2):620-634

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Broad-Band Radio to X-Ray Properties of Seyfert Galaxies     

R. A. Kandalyan  H. M. K. AL-Naimiy 《Astrophysics》2002,45(3):277-287

We report on the statistical analysis of a sample of AGNs (Seyferts and LINERs) selected from an RBSC-NVSS sample of the brightest X-ray sources. The sample is large enough and unbiased for a detailed study of multi-frequency (radio to X-ray) properties of AGN. There are no significant differences in X-ray, optical, far-infrared, and radio powers, core dominance, radio loudness, radio spectral index, and two-point radio-to-optical and optical-to-X-ray spectral indices of Seyfert types 1 and 2. These findings strongly support the unification model, and the observed differences between Sy1 and Sy2 are due to both the variable obscuration and different geometric orientation effects. The correlation between the X-ray and radio emission over many decades is primary and indicates the intrinsically similar origin of both radiations in Seyfert galaxies, powered mainly by AGN, rather than compact starbursts. For Seyfert galaxies we found that the slopes of the relations L _X - L _R and L _X - L _B are flat, which indicate the existence of components unrelated with X-ray. Perhaps only for LINERs is the observed L _X - L _R relation completely due to AGNs. The Sy1, Sy2, and LINER galaxies show different slopes in the relation L _X - L _1.4, and the relative contribution of extended radio components may be the cause of these differences. The possible effects of unresolved extended radio and X-ray components are quantitatively discussed.  相似文献   

Confidence Limits of Evolutionary Synthesis Models     

Miguel Cerviño  Valentina Luridiana 《Astrophysics and Space Science》2002,281(1-2):207-210

The probabilistic nature of the IMF in stellar systems implies that clusters of the same mass and age do not present the same unique values of their observed parameters. Instead they follow a distribution. We address the study of such distributions in terms of their confidence limits that can be obtained by evolutionary synthesis models. These confidence limits can be understood as the inherent uncertainties of synthesis models. We will compare such confidence limits arising from the discreteness of the number of stars obtained with Monte Carlo simulations with the dispersion resulting from an analytical formalism. We give some examples of the effects on the kinetic energy, V–K, EW(Hβ) and multiwavelength continuum. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Properties of galaxy groups in the Sloan Digital Sky Survey – II. Active galactic nucleus feedback and star formation truncation     

Simone M. Weinmann  Frank C. van den Bosch  Xiaohu Yang  H. J. Mo  Darren J. Croton  Ben Moore 《Monthly notices of the Royal Astronomical Society》2006,372(3):1161-1174

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The 2dF Galaxy Redshift Survey: luminosity functions by density environment and galaxy type     

Darren J. Croton  Glennys R. Farrar  Peder Norberg  Matthew Colless  John A. Peacock  I. K. Baldry  C. M. Baugh  J. Bland-Hawthorn  T. Bridges  R. Cannon  S. Cole  C. Collins  W. Couch  G. Dalton  R. De Propris  S. P. Driver  G. Efstathiou  R. S. Ellis  C. S. Frenk  K. Glazebrook  C. Jackson  O. Lahav  I. Lewis  S. Lumsden  S. Maddox  D. Madgwick  B. A. Peterson  W. Sutherland  K. Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(3):1155-1167

We use the 2dF Galaxy Redshift Survey to measure the dependence of the b _J-band galaxy luminosity function on large-scale environment, defined by density contrast in spheres of radius  8  h ⁻¹ Mpc  , and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than   M _{b J}−5log₁₀ h ≲−18.5  . In contrast, cluster regions have a relative excess of very bright early-type galaxies with   M _{b J}−5log₁₀ h ≲−21  . Differences in the mid- to faint-end population between environments are significant: at   M _{b J}−5log₁₀ h =−18  early- and late-type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion that differs strikingly for early- and late-type galaxies. These observed variations, combined with our finding that the faint-end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation.  相似文献