Implications for unified schemes from submillimetre and far-infrared follow-up of radio-selected samples     

Jennifer A. Grimes  Steve Rawlings  Chris J. Willott 《Monthly notices of the Royal Astronomical Society》2005,359(4):1345-1355

We extend our previous analysis which used generalized luminosity functions (GLFs) to predict the number of quasars and galaxies in low-radio-frequency-selected samples as a function of redshift, radio luminosity, narrow-emission-line luminosity and type of unified scheme. Our extended analysis incorporates the observed submillimetre (850-μm) flux densities of radio sources, employs a new method which allows us to deal with non-detections, and focuses on the high-luminosity population. First, we conclude that the submillimetre luminosity L ₈₅₀ of low-frequency-selected radio sources is correlated with the bolometric luminosity L _bol of their quasar nuclei via an approximate scaling relation   L ₈₅₀∝ L ^0.7±0.2_bol  . Secondly, we conclude that there is quantitative evidence for a receding-torus-like physical process for the high-luminosity population within a two-population unified scheme for radio sources; this evidence comes from the fact that radio quasars are brighter in both narrow emission lines and submillimetre luminosity than radio galaxies matched in radio luminosity and redshift. Thirdly, we note that the combination of a receding-torus-like scheme and the assumption that the observed submillimetre emission is dominated by quasar-heated dust yields a scaling relation   L ₈₅₀∝ L ^1/2_bol  which is within the errors of that determined here for radio-selected quasars, and consistent with that inferred for radio-quiet quasars.  相似文献   

Two-fluid Dynamics in Clusters of Galaxies     

Yu-Qing LouNational Astronomical Observatories  Chinese Academy of Sciences  Beijing Department of Physics & Tsinghua Center for Astrophysics 《中国天文和天体物理学报》2005,5(1):6-20

We develop a theoretical formulation for the large-scale dynamics of galaxy clusters involving two spherical ‘isothermal fluids‘ coupled by their mutual gravity and derive asymptotic similarity solutions analytically. One of the fluids roughly approximates the massive dark matter halo, while the other describes the hot gas, the relatively small mass contribution from the galaxies being subsumed in the gas. By properly choosing the self-similar variables, it is possible to consistently transform the set of time-dependent two-fluid equations of spherical symmetry with serf-gravity into a set of coupled nonlinear ordinary differential equations (ODEs). We focus on the analytical analysis and discuss applications of the solutions to galaxy clusters.  相似文献   

Searching for cluster substructure using APM and ROSAT data     

V. Kolokotronis  S. Basilakos  M. Plionis  I. Georgantopoulos 《Monthly notices of the Royal Astronomical Society》2001,320(1):49-60

We present a detailed study of the morphological features of 22 rich galaxy clusters. Our sample is constructed from a cross-correlation of optical     data with X-ray (0.1–2.4 keV) ROSAT pointed observations. We systematically compare cluster images and morphological parameters in an attempt to reliably identify possible substructure in both optical and the X-ray images. To this end, we compute various moments of the optical and X-ray surface-brightness distribution such as the ellipticities, centre-of-mass shifts and ellipsoidal orientations. We assess the significance of our results using Monte Carlo simulations. We find significant correlations between the optical and X-ray morphological parameters, indicating that in both parts of the spectrum it is possible to identify correctly the dynamical state of a cluster. Most of our clusters (17/22) have a good one-to-one correspondence between the optical and the X-ray images, and about 10 appear to have strong indications of substructure. This corresponds to a minimum percentage of order ∼45 per cent, which is in very good accordance with other similar analyses. Finally, five out of 22 systems (∼22 per cent) seem to have distinct subclumps in the optical which are not verified in the X-ray images, and thus are suspect of being due to optical projection effects. These results will serve as a useful guide in interpreting subsequent analyses of large optical cluster catalogues.  相似文献   

ISO LWS observations of planetary nebula fine-structure lines     

X.-W. Liu  M. J. Barlow  M. Cohen  I. J. Danziger  S.-G. Luo  J. P. Baluteau  P. Cox  R. J. Emery  T. Lim  D. Péquignot 《Monthly notices of the Royal Astronomical Society》2001,323(2):343-361

  相似文献   

Distribution of general aerobic heterotrophic bacteria in sediment core taken from the Canadian basin and the Chukchi Sea     

高爱国  陈皓文 《极地研究(英文版)》2008,19(1):14-22

The occurrence percentage and abundance of General Aerobic Hetero- trophic Bacteria （GAB） were determined by using the method of MPN for 182 sub- samples from 10 sediment cores taken from the Canadian basin and the Chukchi Sea at two different culturing temperatures. The results showed that the general occurrence percentage of GAB was quite high, average abundanees of GAB at cultured temperatares of 4℃ and 25℃ were 4.46 ×10^7 and 5.47×10^7 cells·g^-1（wt）, respectively. The highest abundance of GAB occurred at 20 -22 cm section in the sediment. GAB abundances changed among the section of sediments, but there is a trend ： the a-bundances at the middle or lower sections were lower than those at upper section. Cultivation at 25℃ could improve the occurrence percentage and abundances of GAB, which suggests that the increasing of temperature may change the living circum-stances of GAB. The differences of GAB among the latitudes areas indicated that occurrence percentage and abundances of GAB in middle latitude areas were higher than those in the higher or lower latitude areas, and were more obvious at 4℃ than those at 25℃. The GAB abundances in sediment under the shallower water seemed to be low- er than those in sediments under the deeper water and this status was more obvious at 25℃ than that at 4℃.  相似文献   

北赤道流分叉点及南海北部环流的研究进展   总被引：6，自引：0，他引：6  

何映晖  蔡树群  王盛安 《海洋学研究》2009,27(3):74-84

介绍了北赤道流分叉点、南海北部环流的一些研究成果,并就黑潮对南海的影响所作的研究进行了回顾.北赤道流分叉点的位置对于北赤道流系水体疏运变化及在黑潮和MC之间水体、热量、盐度输运的分配中起着重要的作用.北赤道流分叉点位置约在14.6°N上,分叉点位置随深度增加而北移.分叉点有明显的季节变化和年际变化,在春、夏季向南移动,而在秋、冬季则向北移动.年际变化与ENSO现象相关紧密,在El Nio事件NEC分叉纬度处于最北端,在La Nio事件处于最南端.对于分叉点位置的定量化研究,仍然需要更多的观测结果进行研究.季风和黑潮是影响南海北部环流的两种主要因素.南海北部上层流场主要由广东沿岸流、黑潮入侵流套、东沙海流、南海暖流和吕宋海流组成.除海盆、次海盆尺度环流外,受季风、黑潮和地形等因素的影响,南海表现出多涡结构.通过近些年的卫星观测和数值模拟的结果,人们对南海中尺度涡的认识大大加深,但要想模拟出风应力形成涡的机制,还需要提高风场和模式的分辨率.由于观测资料的限制,对南海流场的垂直结构、以及春-秋季季风转相时期的流场结构等还研究得较少.吕宋海峡水交换是西太平洋对南海影响的主要途径.黑潮在吕宋海峡附近的形变一直是有争议的热点问题,目前对于黑潮入侵有3种观点:(1) 认为黑潮经过吕宋海峡形成流套结构,并分离出中尺度涡影响南海流场、水团结构;(2) 认为黑潮有一直接分支分离出来进入南海形成黑潮分支;(3) 认为吕宋海峡水交换不属于以上两种情况,西太平洋对南海的水团输送另有机制.北赤道流分叉点在对黑潮的水体、热量、盐度输运的分配中起着重要的作用,黑潮对南海北部环流的影响可能与NEC的分叉点位置有关,但目前对NEC的分叉点位置与南海北部环流相关性的研究甚少.最后提出了对未来加强该方面研究的一些展望.  相似文献   

A deeper search for the progenitor of the Type Ic supernova 2002ap     

R. M. Crockett  S. J. Smartt  J. J. Eldridge  S. Mattila  D. R. Young  A. Pastorello  J. R. Maund  C. R. Benn  I. Skillen 《Monthly notices of the Royal Astronomical Society》2007,381(2):835-850

  相似文献   

CJF-12型冲击反循环钻机在浅海施工工艺          下载免费PDF全文

张亚东  王玉吉 《山东国土资源》2007,23(2):48-49

在浅海岸边进行钻机作业,由于海平面水位不稳定,采用6BS反循环泵已不合适。在工作实践中,将原施工工艺改进为气举反循环,此方法不仅没有降低原钻机的施工性能,而且快捷、方便,经济效益显著。  相似文献   

On the origin of the kinematical differences between the stellar halo and the old globular cluster system in the Large Magellanic Cloud     

Kenji Bekki 《Monthly notices of the Royal Astronomical Society》2007,380(4):1669-1677

  相似文献   

X-ray emission from planetary nebulae calculated by 1D spherical numerical simulations     

M. Akashi  Noam Soker  Ehud Behar  John Blondin 《Monthly notices of the Royal Astronomical Society》2007,375(1):137-144

We calculate the X-ray emission from both constant and time-evolving shocked fast winds blown by the central stars of planetary nebulae (PNe) and compare our calculations with observations. Using spherically symmetric numerical simulations with radiative cooling, we calculate the flow structure and the X-ray temperature and luminosity of the hot bubble formed by the shocked fast wind. We find that a constant fast wind gives results that are very close to those obtained from the self-similar solution. We show that in order for a fast shocked wind to explain the observed X-ray properties of PNe, rapid evolution of the wind is essential. More specifically, the mass-loss rate of the fast wind should be high early on when the speed is  ∼300–700 km s⁻¹  , and then it needs to drop drastically by the time the PN age reaches ∼1000 yr. This implies that the central star has a very short pre-PN (post-asymptotic giant branch) phase.  相似文献