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81.
The structure of the Galactic bar 总被引：1，自引：0，他引：1
We present a deep near-infrared wide-angle photometric analysis of the structure of the inner Galactic bar and central disc. The presence of a triaxial structure at the centre of the Galaxy is confirmed, consistent with a bar inclined at 22°± 55 from the Sun—Galactic Centre line, extending to approximately 2.5 kpc from the Galactic Centre and with a rather small axis ratio. A feature at ℓ=−98 not aligned with this triaxiality suggests the existence of a second structure in the inner Galaxy, a double triaxiality or an inner ring. We argue that this is likely to be the signature of the end of the Galactic bar, at approximately 2.5–3 kpc, which is circumscribed by an inner pseudo-ring. No thick dust lane preceding the bar is detected and a hole in the dust distribution of the disc inside the bar radius is inferred. 相似文献
82.
通过铸体薄片、AxioVision图像分析、岩芯常规分析、地层水测试等方法,在明确了碳酸盐胶结物类型的基础上,采用多方法进行了碳酸盐胶结物含量的测定,探讨了准噶尔盆地车排子地区北部沙湾组碳酸盐胶结物差异性分布控制因素,并揭示了其对储层物性、油水分布的影响。研究表明,车北地区沙湾组储层中发育大量的早期碳酸盐胶结物,不均匀充填部分原生粒间孔,具有强烈的非均质性;在岩芯常规测定碳酸盐胶结物含量的基础上,利用多次数、多视域的AxioVision图像分析补充测定了碳酸盐胶结物含量,与岩芯常规测定结果对比相对误差-0.14,弥补了数据点的不足。碳酸盐胶结物含量平面上具有“北高南低”的差异性分布特征,胶结物形成于封闭性好、水体交替停滞的还原环境中,地层水Ca2+含量的差异决定了碳酸盐胶结物分布的差异,而地层水Ca2+含量的差异主要受古地貌控制,古高地水体较浅易富集Ca2+是CaCO3沉淀的良好场所,沉积微相在局部井区起到一定的控制作用。碳酸盐胶结物差异性导致研究区储层物性具有“双峰值”特征,并造成了高黏超稠油油藏复杂的油水分布关系。 相似文献
83.
准噶尔盆地车排子周缘白垩系底部不整合面的形成及其油气输导作用 总被引：2，自引：0，他引：2
准噶尔盆地白垩系底部不整合面在车排子周缘大面积分布,是其二叠系和侏罗系的油源进入白垩系和新近系储层的重要通道之一,对其微观结构和几何形态的研究对油气勘探有重要意义。利用岩心、测井、岩屑录井等资料识别出不整合面的三层结构,对不整合面之上的岩石、风化粘土层及不整合面之下的半风化壳进行深入研究,探讨白垩系底部不整合面的形成过程,明确不整合面三层结构的油气输导作用。不整合面的形成可划分为抬升风化期、剥蚀搬运期、下降沉积期和成岩压实期4个阶段。研究表明风化粘土层上下的岩石具有高效的油气输导能力,风化粘土层在断裂不发育区可作为油气局部盖层。油气沿白垩系底部不整合面从东南向西北部的车排子凸起运移。 相似文献
84.
L. Kohoutek 《Astronomische Nachrichten》1994,315(3):235-244
In the first part of this study of PN towards the galactic centre we present the discovery of 24 new planetary nebulae found on the objective-prism spectra in three ESO fields (Table 1 - parameters of the survey, Tables 3 and 4 - new objects). The observations of those objects are listed in Table 5. Besides, we give the classification and the positions of known objects in this area (Table 2). 相似文献
85.
Nicholas J. Rattenbury Shude Mao 《Monthly notices of the Royal Astronomical Society》2006,365(3):792-800
Interferometers from the ground and space will be able to resolve the two images in a microlensing event. This will at least partially lift the inherent degeneracy between physical parameters in microlensing events. To increase the signal-to-noise ratio, intrinsically bright events with large magnifications will be preferentially selected as targets. These events may be influenced by finite source size effects both photometrically and astrometrically. Using observed finite source size events as examples, we show that the fringe visibility can be affected by ∼5–10 per cent, and the closure phase by a few degrees – readily detectable by ground and space interferometers. Such detections will offer unique information about the lens–source trajectory relative to the baseline of the interferometers. Combined with photometric finite source size effects, interferometry offers a way to measure the angular sizes of the source and the Einstein radius accurately. Limb-darkening changes the visibility by a small amount compared with a source with uniform surface brightness, marginally detectable with ground-based instruments. We discuss the implications of our results for the plans to make interferometric observations of future microlensing events. 相似文献
86.
John E. Everett Ellen G. Zweibel Robert A. Benjamin Dan McCammon Lindsay Rocks Donald P. Cox John S. Gallagher 《Astrophysics and Space Science》2007,311(1-3):105-110
The ROSAT All-Sky Survey revealed soft X-ray emission on kiloparsec scales towards the Galactic center. Separately, it has
also been observed that the cosmic ray intensity (measured via γ-ray emission) rises only very slowly towards the center of the Galaxy, counter to expectations based on the greater number
of cosmic ray sources there. A thermal and cosmic-ray driven wind could potentially explain both of these observations. We
find that a cosmic-ray and thermally driven wind fits the X-ray observations well; in fact, a wind fits significantly better
than an earlier-proposed static-polytrope gas model. 相似文献
87.
88.
89.
Shude Mao Martin C. Smith P. Wo&#;niak A. Udalski M. Szyma&#;ski M. Kubiak G. Pietrzy&#;ski I. Soszy&#;ski K. &#;ebru&#; 《Monthly notices of the Royal Astronomical Society》2002,329(2):349-354
We describe the discovery of the longest microlensing event ever observed, OGLE-1999-BUL-32, also independently identified by the MACHO collaboration as MACHO-99-BLG-22. This unique event has an Einstein radius crossing time of 640 d. The high-quality data obtained with difference image analysis shows a small but significant parallax signature. This parallax effect allows one to determine the Einstein radius projected on to the observer plane as . The transverse velocity projected on to the observer plane is about 79 km s−1 . We argue that the lens is likely to have a mass of at least a few solar masses, i.e. it could be a stellar black hole. The black hole hypothesis can be tested using the astrometric microlensing signature with the soon-to-be installed Advanced Camera for Surveys on board the Hubble Space Telescope . Deep X-ray and radio images may also be useful for revealing the nature of the object. 相似文献
90.
The behavior of a river plume in Suo-Nada, Japan, has been studied using a primitive equation numerical model, the Princeton
Ocean Model. Special attention has been paid to the current structure and behavior of the anticyclonic eddy (bulge) induced
by high freshwater inflow changing on a timescale of one week. First, the freshwater is supplied from a river to a rectangular
basin with a simple topography. When the river discharge subsides after reaching its peak value, the bulge propagates upstream
(i.e., opposite to the direction of the Kelvin wave propagation). Next, the freshwater is supplied from eight major rivers
to the basin with realistic topography. The less saline water mass in the southern part of Suo-Nada propagates to the west
(i.e., upstream) after the river discharge subsides. This is consistent with an observed phenomenon, viz., that the less saline
water mass appears in the western part of Suo-Nada, suggesting that the upstream propagation of the bulge is possible in the
real ocean. Finally, the cause of the upstream propagation is considered. Onshore currents appear in the bottom layer beneath
the bulge, propagating upstream. They produce an anticyclonic barotropic eddy due to the conservation of potential vorticity.
The current component associated with the eddy crosses normally to the isohaline in the upper layer, and therefore transports
the bulge upstream. No other current component (such as surface current velocity minus vertically-averaged value) is responsible
for the upstream propagation of the bulge.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献