A dusty torus around the luminous young star LkH alpha101

A star forms when a cloud of dust and gas collapses. It is generally believed that this collapse first produces a flattened rotating disk, through which matter is fed onto the embryonic star at the centre of the disk. When the temperature and density at the centre of the star pass a critical threshold, thermonuclear fusion begins. The remaining disk, which can still contain up to 0.3 times the mass of the star, is then sculpted and eventually dissipated by the radiation and wind from the newborn star. But this picture of the structure and evolution of the disk remains speculative because of the lack of morphological data of sufficient resolution and uncertainties regarding the underlying physical processes. Here we present images of a young star, LkH alpha101, in which the structure of the inner accretion disk is resolved. We find that the disk is almost face-on, with a central gap (or cavity) and a hot inner edge. The cavity is bigger than previous theoretical predictions, and we infer that the position of the inner edge is probably determined by sublimation of dust grains by direct stellar radiation, rather than by disk-reprocessing or viscous-heating processes as usually assumed.     

Investigation of the obscuring circumnuclear torus in the active galaxy Mrk231

Active galaxies are characterized by prominent emission from their nuclei. In the 'unified' view of active galaxies, the accretion of material onto a massive compact object--now generally believed to be a black hole--provides the fundamental power source. Obscuring material along the line of sight can account for the observed differences in the nuclear emission, which determine the classification of AGN (for example, as Seyfert 1 or Seyfert 2 galaxies). Although the physical processes of accretion have been confirmed observationally, the structure and extent of the obscuring material have not been determined. Here we report observations of powerful hydroxyl (OH) line emissions that trace this obscuring material within the circumnuclear environment of the galaxy Markarian 231. The hydroxyl (mega)-maser emission shows the characteristics of a rotating, dusty, molecular torus (or thick disk) located between 30 and 100 pc from the central engine. We now have a clear view of the physical conditions, the kinematics and the spatial structure of this material on intermediate size scales, confirming the main tenets of unification models.     

木卫一等离子体环中冷热离子的轨迹

通过模拟木卫一等离子体环中冷热离子的轨迹来分析离心力对冷热离子作用的大小,说明冷离子在离心力的约束下沿着磁力线来回反射,不可能进入木星大气层,而离心力对热离子运动的影响不大.木卫一等离子体环主要由高密度的冷等离子体组成,因此还需要一个能使冷离子离开木卫一等离子体环进入木星大气层的机制,使它能够引发木卫一尾迹极光的发射.     

风沙条件下颗粒对翼型流动分离的影响

运用延迟脱体涡模拟(delayed detached eddy simulation,DDES)技术对NREL S809三维翼型在洁净空气环境中和在不同直径颗粒环境下进行了数值模拟,由此预测了风沙环境下颗粒对翼型绕流分离的影响.研究结果表明:当攻角为8°时,DDES捕捉到了翼型吸力面的涡脱落现象,并且颗粒的加入显著地改变了翼型吸力面的涡脱规律,使得尾涡范围扩大、耗散更快,然而随着颗粒直径的增大,尾涡也逐渐恢复到接近洁净空气时的状态;当攻角较小(6°)时,翼型表面没有发生流动分离,颗粒的加入对流场的影响很小;当攻角较大(12°)时,颗粒对翼型绕流的影响也很小;不同攻角下颗粒对翼型升力系数有不同程度的影响.分析不同攻角下颗粒对翼型表面流动分离的影响规律表明:S809翼型绕流情况受颗粒影响最严重的攻角在7°~10°.     

The inner jet of an active galactic nucleus as revealed by a radio-to-gamma-ray outburst

Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV gamma-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images.     

环面自映射在拓扑空间中的提升

设f:S1×S1→S1×S1是环面上的连续映射;F:R×R→R×R是平面到自身的连续映射;E*:R×R→S1×S1是平面到环面上的复迭映射。利用提升映射的特征和复迭映射的运算,给出了环面这类映射提升的相关的性质。     

环面自映射在拓扑空间中的提升

设f:S1×S1→S1×S1是环面上的连续映射;F:R×R→R×R是平面到自身的连续映射;E*:R×R→S1×S1是平面到环面上的复迭映射.利用提升映射的特征和复迭映射的运算,给出了环面这类映射提升的相关的性质.     

筒子图Pn×Cm的粘连度

讨论了筒子图Pn×Cm的性质和粘连度.     

平面闭曲线上扁形椭圆环面的全平均曲率——Willmore猜想的一个例证

给出了W illmore猜想的一个例证,说明平面闭曲线上扁形椭圆环面的全平均曲率M2H2dA≥2π2p2,其中p为椭圆的短轴与长轴之比.     

分子云NGC7538中心源的红外辐射及成协气体的热平衡

本文根据NGC7538的红外和分子谱线观测结果,对红外源的热结构及成协气体的热平衡进行了计算和分析。得出尘埃温度随半径的分布T_d a r~(-0.36)其峰值温度略高于已有观测结果,并发现除中心源附近区域外,大部分区域内不再满足尘埃通过碰撞向气体输入能量的基本条件。本文计算了NGC7538气体的冷却串及多种机制的加热作用,结果表明宇宙线、坍缩及双极扩散等机制的加热率相对较小,而尘埃通过光电作用对气体的加热可能是气体的重要热源。     

含有双温非热离子的尘埃等离子体中的非线性尘埃声孤波

使用约化摄动法得到了含有双温非热离子的尘埃等离子体中的KdV方程.结果表明,双温满足非热分布的离子会严重影响着尘埃声孤波的结构,而且,该体系中稀疏形孤波与压缩形孤波共存.     

圆环面截交线投影的参数方程及其在计算机绘图中的应用

本文用辅助面法推导出了圆环面截交线投影的参数方程,并应用这一参数方程,在计算机上快速、准确地绘出了圆环面及其有关零件表面截交线的投影。     

量子环面上的导子李代数模的导子

设q是p次本原单位根,L是两个变量的量子环面Cq上的导子李代数, W=Fαg (V)是由函子Fαg 作用在有限维gl2-模V上诱导的L-模。那么李代数L到其模W的导子除几种情形外都是内导子,且由此1-上同调群H1(L, W)在大多数情形下是平凡的。     

筒子图Pn×Cm的粘连度

讨论了筒子图Pn×Cm的性质和粘连度．     

Magnetic support of the optical emission line filaments in NGC 1275

The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments, which are plausibly in excess of 10(8) years old. The filaments are dragged out from the centre of the galaxy by radio-emitting 'bubbles' rising buoyantly in the hot intracluster gas, before later falling back. They act as markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding extremely hot (4 x 10(7) K) gas has been unclear. Here we report observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.     

含有双温非热离子的热尘埃等离子体中的尘埃声孤波

使用约化摄动方法得到含有双温非热离子的无磁化热尘埃等离子体中的KdV方程.研究结果表明,尘埃流体的温度会严重影响尘埃声孤波的结构,而且允许稀疏形孤波与压缩形孤波共存.     

含有非热离子及尘粒电荷变化的尘埃等离子体中的KP方程

使用约化摄动法得到含有非热离子、尘粒荷电变化的热尘埃等离子体中的KP方程.结果表明,非热离子分布会严重影响尘粒的电荷数.而且,高阶横向扰动的存在使得尘埃声孤波的振幅减小,而宽度增大.同时,该体系中稀疏形孤波和压缩形孤波共存.