The Qso Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution?     

Julia Scharwächter  Andreas Eckart  Susanne Pfalzner  Jens Zuther  Melanie Krips  Eva Schinnerer  Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):101-106

I Zw 1 and 3C 48 are two neighboring template objects at a later stage of the hypothesized merger-driven evolutionary sequence from ultra-luminous infrared galaxies (ULIRGs) to quasi-stellar objects (QSOs). Since galaxy mergers are assumed to trigger the evolution, it is important to confirm the merger properties of transitionary objects. Using multi-wavelength observations and N-body simulations, the merger histories of I Zw 1 and 3C 48 have been investigated in two separate case studies. Here, the results from both studies are compared and their relevance for the evolutionary hypothesis is discussed.This research is partly based on observations with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) under projects 67.B-0009 and 67.B-0019.  相似文献   

The τ Herculid meteor shower and Comet 73P/Schwassmann–Wachmann 3     

P. A. Wiegert  P. G. Brown  J. Vaubaillon  H. Schijns 《Monthly notices of the Royal Astronomical Society》2005,361(2):638-644

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A radio study of neutral gas and dust in the radio galaxy 3C 293     

R.J. Beswick  A. Pedlar†  A.J. Holloway 《Monthly notices of the Royal Astronomical Society》2002,329(3):620-628

We have observed broad H  i absorption in the radio galaxy 3C 293 using Multi-Element Radio Linked Interferometric Network (MERLIN) at 0.2-arcsec angular resolution and the Giant Meterwavelength Radio Telescope (GMRT) at arcsec resolution. Extensive H  i is found in absorption across the centre of this peculiar radio galaxy, allowing a detailed study of the dynamics of the neutral gas on linear scales down to ∼160 pc. In optical depth position–velocity diagrams across the central few kpc we detect a distinct velocity gradient of 179 km s⁻¹ arcsec⁻¹ associated with the broad absorption. This is interpreted as a ring of neutral gas rotating around the suspected position of the active galactic nucleus (AGN) . The radius of this high velocity gradient ring is found to be >0.74 arcsec (600 pc), implying an upper limit upon the enclosed mass of     , assuming a near edge-on disc with an inclination of i . The optical depth of H  i is mapped across the entire central region of 3C 293 showing enhancements of a factor of 4 in the areas that are co-spatial with dust lanes seen in Hubble Space Telescope ( HST ) imaging of this galaxy.  相似文献   

Detecting subtle hydrochemical anomalies with multivariate statistics: an example from ‘homogeneous’ groundwaters in the Great Artesian Basin,Australia     

Bethany O'Shea  Jerzy Jankowski 《水文研究》2006,20(20):4317-4333

The major ion composition of Great Artesian Basin groundwater in the lower Namoi River valley is relatively homogeneous in chemical composition. Traditional graphical techniques have been combined with multivariate statistical methods to determine whether subtle differences in the chemical composition of these waters can be delineated. Hierarchical cluster analysis and principal components analysis were successful in delineating minor variations within the groundwaters of the study area that were not visually identified in the graphical techniques applied. Hydrochemical interpretation allowed geochemical processes to be identified in each statistically defined water type and illustrated how these groundwaters differ from one another. Three main geochemical processes were identified in the groundwaters: ion exchange, precipitation, and mixing between waters from different sources. Both statistical methods delineated an anomalous sample suspected of being influenced by magmatic CO₂ input. The use of statistical methods to complement traditional graphical techniques for waters appearing homogeneous is emphasized for all investigations of this type. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

2000年度上海天文台卫星激光测距观测报告     

杨福民  张忠萍  陈婉珍  陈菊平  徐永平  李鑫 《中国科学院上海天文台年刊》2002,(1)

介绍了 2 0 0 0年度上海天文台卫星激光测距观测和系统的改进情况  相似文献   

小型氢原子钟监控系统的研制     

陈丛军  林传富 《中国科学院上海天文台年刊》2007,(1):151-159

该文介绍了目前上海天文台正在研制的小型氢原子钟的监控系统。它可监控氢钟的工作情况，实现氢钟的自动启闭、参数自动检测、自动报警，可控制综合器的频率变化、微波腔温度、氢离子流的大小。  相似文献   

手持式激光测距仪前级接收通道的相关问题研究   总被引：2，自引：0，他引：2  

夏界宁 《大地测量与地球动力学》2007,27(Z1):93-95

介绍了手持式激光测距仪前置放大电路的设计方法,并且针对便携式设备供电的特殊性,给出了单电源供电放大电路的解决方案,较好地解决了前级接收通道电路设计的相关问题.  相似文献   

Relativistic models and the jet velocity field in the radio galaxy 3C 31   总被引：1，自引：0，他引：1  

R. A. Laing  A. H. Bridle 《Monthly notices of the Royal Astronomical Society》2002,336(1):328-352

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2-D or 3-D interpretation of conductivity anomalies: example of the Rhine-Graben conductivity anomaly     

M. Menvielle  P. Tarits 《Geophysical Journal International》1986,84(2):213-226

Summary. Evidence of a conductivity anomaly in the Rhine-Graben was first given about 15 years ago and consequently led to the definition of various models of induction in the region for periods ranging from a few minutes to a few hours. These models reflect two antagonistic ways of explaining the observed anomalous variations of the magnetic field: direct induction in a two-dimensional (2-D) structure or static distortion of telluric currents by the resistive crystalline Vosges (France) and Schwarzwalde (Germany) massifs. We discuss the two approaches using a simple formalism. In particular, we show that the self-induction related to the anomalous currents flowing in the Rhine-Graben is negligible for periods larger than 1000 s, and that, even though the static distortion of telluric currents does account for the observed anomaly, 2-D models can explain some of its features. We also show how the channelled currents are induced in the large sedimentary basins surrounding the area under study.
An experimental verification of this result is given.  相似文献   

Models of the formation of the solar nebula     

Patrick Cassen  Audrey Summers 《Icarus》1983,53(1):26-40

Models of the collapse of a protostellar cloud and the formation of the solar nebula reveal that the size of the nebula produced will be the larger of $\text{R}{}_{\mathrm{<mtext>CF</mtext>}}\text{≡ J}{}^2\text{/k}{}^2\text{GM}{}^3\text{and}\text{R}{}_{\mathrm{<mtext>V</mtext>}}\text{≡ (GMv/2c}{}_{\mathrm{<mtext>c</mtext>}}{}^3\text{)}\text{1}\text{2}$ (where J, M, and c_s are the total angular momentum, total mass, and sound speed of the protosetellar material; G is the gravitational constant; k is a number of order unity; and v is the effective viscosity in the nebula). From this result it can be deduced that low-mass nebulas are produced if P ≡ (R_V/R_CF)² ? 1; “massive” nebulas result if P ? 1. Gravitational instabilities are expected to be important for the evolution of P ? 1 nebulas. The value of J distinguishes most current models of the solar nebula, since P ∝ J^?4. Analytic expressions for the surface density, nebular mass flux, and photospheric temperature distributions during the formation stage are presented for some simple models that illustrate the general properties of growing protostellar disks. It does not yet seem possible to rule out either P ? 1 or P < 1 for the solar nebula, but observed or possible heterogeneities in composition and angular-momentum orientation favor P < 1 models.  相似文献