排序方式： 共有36条查询结果，搜索用时 15 毫秒
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M. T. Crosta A. Vecchiato F. de Felice M. G. Lattanzi B. Bucciarelli 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):209-218
In this article we outline the structure of a general relativistic astrometric model which has been developed to deduce the position and proper motion of stars from 1 µarcsecond optical observations made by an astrometric satellite orbiting around the Sun. The basic assumption of our model is that the Solar System is the only source of gravity, hence we show how we modeled the satellite observations in a many-body perturbative approach limiting ourselves to the order of accuracy of (v/c)2. The microarcsecond observing scenario outlined is that for the GAIA astrometric mission. 相似文献
33.
Spiral galaxies show axial symmetry and an intrinsic 2D-chirality. Environmental effects can influence the chirality of originally
isolated stellar systems and a progressive loss of chirality can be recognized in the Hubble sequence. We point out a preferential
modality for genetic galaxies as in microscopic systems like aminoacids, sugars or neutrinos. This feature could be the remnant
of a primordial symmetry breaking characterizing systems at all scales. 相似文献
34.
P. Lattanzi 《Mineralium Deposita》1990,25(1):S86-S89
Recent O-isotope and fluid inclusion studies have provided evidence on the nature of the fluids associated with the late-Alpine quartz-gold deposits of the Monte Rosa district. The most abundant inclusions in quartz from these deposits contain a low salinity aqueous fluid (about 2% to 10% wt. NaCl eq.), and a CO2 phase (usually less than 20% mol), in places with minor methane. CO2 densities and total homogenization temperatures vary widely throughout the district, reflecting diverse conditions of trapping (P = 1 to 3 kb, T = 300° to 450°C). At Miniera dei Cani, unmixing between CO2-rich and H2O-rich fluids possibly occurred. A second type of inclusion contains an aqueous brine without recognizable CO2, and is especially abundant at Val Toppa. O-isotope studies suggest that fluids were largely equilibrated in a metamorphic environment. It is concluded that the gold-related fluids in the district were mainly of a metamorphic nature; at Val Toppa, both isotopic and fluid inclusion data point to contributions of unexchanged meteoric waters. Mechanisms of gold transport and precipitation are less contrained. A possible model involves transport of gold as bisulfide complexes, and precipitation due to one or more of the following processes: decrease of sulfur activity due to precipitation of sulfides, wall-rock reaction, cooling/dilution, and/or fluid unmixing. 相似文献
35.
We present the results of a program to obtain an accurate (better than 100 mas) astrometry of HST images of NGC 1068 and consequently
a direct registration with radio images. The optical peak seen in the HST images is located at α = 02h42m40.711s, δ = -00°00′47.81
(J2000, FK5), with an error of 80 mas. The hidden nucleus, as determined by HST imaging polarimetry, falls at α = 02h42m40.710s,
δ = -00°00′48.11. It is offset toward the South, i.e. along the radio axis, with respect to the inverted spectrum radio component,
S1, by 170 mas (12 pc). This does not rule out that S1 is indeed associated with the obscuring torus and the central engine,
but suggests that the nucleus of NGC 1068 might be radio silent or its emission absorbed also at radio wavelengths.
An anti-correlation between radio and optical emission is revealed; the radio jet lies on a region of relatively low optical
emission and is surrounded by line-emitting clouds. These results can be understood as due the interaction between the jet
and the surrounding medium. The outflowing plasma is sweeping and heating the interstellar gas causing the line-emission to
be highly enhanced along the edges of the radio jet. It appears that the morphology of the Narrow Line Region of NGC 1068
is dominated by the presence of a radio outflow, as already revealed by HST observations of several Seyfert galaxies with
extended radio emission.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
36.
G. Chiumiento M. G. Lattanzi G. Massone R. Morbidelli R. Pannunzio M. Sarasso 《Astrophysics and Space Science》1991,177(1-2):93-96
We present optical positions in the improved IAU System at the standard epoch J2000.0 of some extragalactic radio sources obtained at Torino Astronomical Observatory. The primary reference stars are taken from the Carlsberg Automatic Meridian Catalogues 1 and 2 (CAMC). 相似文献