A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar   总被引：1，自引：0，他引：1  

Eric Emsellem  Paul Goudfrooij  Pierre Ferruit 《Monthly notices of the Royal Astronomical Society》2003,345(4):1297-1312

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北部湾北部海上油田发现历程     

钟铿  潘其云 《南方国土资源》1997,(2)

北部湾北部海上油田的开发工作始于５０年代，６０～７０年代作了大量地质工作。改革开放后，油气勘查取得突破性进展。累计发现油气构造６个，含油面积超过４０ｋｍ２，石油地质储量约４亿ｔ，已开发油田２个，揭开我国南方油气资源开发序幕  相似文献   

新疆阿尔泰哈巴河一带古生代火山岩的形成与演化     

Zhang Chuanling 《地球科学与环境学报》1997,(1)

文中详细地论述了新疆阿尔泰哈巴河一带古生代火山岩的地质、岩石化学、稀土元素地球化学特征。将其分为三个类型，认为火山岩是在陆缘裂陷槽的区域构造背景下发生和演化的。对各类型火山岩岩浆来源，上升模式也做了初步讨论。  相似文献   

利用历史有感地震目录（M≥3（1／2））研究华北地区地震活动性特征          下载免费PDF全文

《地震地质》1994,16(4):373

对新编的华北地区历史有感地震目录（３（１／２）≤Ｍ＜４（１／２））的精度和可信度进行了讨论。认为该地震目录从１４８４年后的记载率较高，它的发震时间、震中位置和震级的精度基本可以满足研究历史地震活动性的需要。它与中国地震目录（Ｍ≥４（３／４））比较，补充了相当数量的３（１／２）≤Ｍ≤４（１／２）的地震。利用历史有感地震目录分析了华北北部部分６级以上的历史地震，结果表明，这些地震在强震发生前具有明显的空区、条带、地震活动性增强、平静等前兆特征，同时，也显示了某些强＊发生前的前震活动和主震之后起伏的强余震活动  相似文献   

西宁盆地泥石流类型及其防治意见     

洪文之  徐旭 《青海国土经略》1997,(1)

概略地叙述了西宁地区的泥石流形成条件和形成机理,并将西宁地区泥石流划分为稀性泥石流类及泥石质泥石流种类。在此基础上提出防治泥石流灾害的意见。  相似文献   

Testing the circumstellar disc hypothesis: a search for H₂ outflow signatures from massive young stellar objects with linearly distributed methanol masers     

J. M. De Buizer 《Monthly notices of the Royal Astronomical Society》2003,341(1):277-298

The results of a survey searching for outflows using near-infrared imaging are presented. Targets were chosen from a compiled list of massive young stellar objects associated with methanol masers in linear distributions. Presently, it is a widely held belief that these methanol masers are found in (and delineate) circumstellar accretion discs around massive stars. If this scenario is correct, one way to test the disc hypothesis is to search for outflows perpendicular to the methanol maser distributions. The main objective of the survey was to obtain wide-field near-infrared images of the sites of linearly distributed methanol masers using a narrow-band 2.12-μm filter. This filter is centred on the  H₂ v = 1–0 S(1)  line; a shock diagnostic that has been shown to successfully trace CO outflows from young stellar objects. 28 sources in total were imaged of which 18 sources display H₂ emission. Of these, only two sources showed emission found to be dominantly perpendicular to the methanol maser distribution. Surprisingly, the H₂ emission in these fields is not distributed randomly, but instead the majority of sources are found to have H₂ emission dominantly parallel to their distribution of methanol masers. These results seriously question the hypothesis that methanol masers exist in circumstellar discs. The possibility that linearly distributed methanol masers are instead directly associated with outflows is discussed.  相似文献   

NGC 1883: a neglected intermediate-age open cluster located in the outskirts of the Galactic disc     

Giovanni Carraro  Gustavo Baume  Sandro Villanova 《Monthly notices of the Royal Astronomical Society》2003,343(2):547-551

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Hydrated sulphuric acid in dense molecular clouds     

Flavio Scappini  Cesare Cecchi-Pestellini  Harvey Smith  William Klemperer  Alexander Dalgarno 《Monthly notices of the Royal Astronomical Society》2003,341(2):657-661

We consider sulphur depletion in dense molecular clouds, and suggest hydrated sulphuric acid, H₂SO₄ ·  n H₂O, as a component of interstellar dust in icy mantles. We discuss the formation of hydrated sulphuric acid in collapsing clouds and its instability in heated regions in terms of the existing hot core models and observations. We also show that some features of the infrared spectrum of hydrated sulphuric acid have correspondence in the observed spectra of young stellar objects.  相似文献   

Erratum: Radio-emitting component kinematics in SS433     

《Monthly notices of the Royal Astronomical Society》2003,344(1):336-336

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Non-Sobolev modelling of radiation-pressure-driven flows in active galactic nuclei     

Doron Chelouche  Hagai Netzer 《Monthly notices of the Royal Astronomical Society》2003,344(1):223-232

We present a new general scheme for calculating the structure and dynamics of radiation-pressure-driven photoionized flows. The new method goes one step beyond the Sobolev approximation. It involves a numerical solution of the radiative transfer in absorption lines, including the effects of differential expansion and line interactions such as line locking and blanketing. We also present a new scheme for calculating the radiation pressure due to trapped line photons in finite, differentially expanding flows. We compare our results for the radiation pressure force with those obtained using the Sobolev approximation and show the limitations of the latter. In particular, we demonstrate that the Sobolev method gives a poor approximation near discontinuity surfaces and its neglect of line blanketing can lead to erroneous results in high-velocity flows. We combine the newly calculated radiation pressure force with self-consistent photoionization and thermal calculations to study the dynamics and spectral features of broad absorption-line flows and highly ionized gas flows in active galactic nuclei (AGN). A comparison with Sobolev-type calculations shows that the latter overestimates the terminal velocity of the flow and, conversely, underestimates its opacity. We also show that line locking on broad emission lines can have a significant effect on the dynamics and spectral features of AGN flows.  相似文献