银河系的秘密

银河系虽是我们的家,但它仍有许多大问题有回答。陋着天文学家对可观测宇宙边缘处星系的不断深入研究,你可能队内银河系对于我们而言已经没有秘密了。其实不然。问题就在于地球所环绕的太阳是一颗处于银河系外围旋臀边缘上的普通恒星,于是我们也就无法获得可以鸟瞰银河系的视野。这就有点像在浓雾天同时公交卡里又公午剩下2元钱的情况下要摸清整个上海一样。     

Geometry of Broad Line Regions of Active Galactic Nuclei

It has long remained an open question as to the geometry of the broad line region （BLR） in active galactic nuclei （AGNs）. The reverberation mapping technique which measures the response of the broad emission lines to the ionizing continuum, when combined with multiwavelength continuum fitted by sophisticated accretion disks, provides a way of probing the BLR geometry. We analyze a sample of 35 AGNs, which have been monitored by the reverberation mapping campaign. In view of energy budget, the reverberation-based BH masses are found to be in agreement with those obtained by accretion disk models in two thirds of the present sample while the reverberation mapping methods underestimate the BH masses in about one third of objects, as also suggested by CoUin et al. in a recent work. We point out that there are obviously two kinds of BLR geometry, which are strongly dependent on the Eddington ratio, and separated by the value LBol/LEdd - 0.1. These results prefer a scenario of the disk and wind configuration of the BLR and identify the Eddington ratio as the physical driver regulating the wind in the BLR.     

Growth of Black Holes and Their Host Spheroids in （Sub）mm-loud High-Redshift QSOs

We study the growth of black holes and stellar population in spheroids at high redshift using several （sub）mm-loud QSO samples. Applying the same criteria established in an earlier work, we find that, similar to IR QSOs at low redshift, the far-infrared emission of these （sub）mm-loud QSOs mainly originates from dust heated by starbursts. By combining low-z IR QSOs and high-z （sub）mm-loud QSOs, we find a trend that the star formation rate （M＊） increases with the accretion rate （Mace）. We compare the values of M＊/Macc for submm emitting galaxies （SMGs）, far-infrared ultraluminous/hypeduminous QSOs and typical QSOs, and construct a likely evolution scenario for these objects. The （sub）mm-loud QSO transition phase has both high Macc and M＊ and hence is important for establishing the correlation between the masses of black holes and spheroids.     

宇宙早期的年轻致密星系

4月29日,在“哈勃”空间望远镜的帮助下。天文学家们观测到了一群年轻的、致密得令人吃惊的星系,每个只有5000光年大小,但是质量却达到了2万亿倍太阳质量。相比之下,我们的银河系直径约为20万光年,质量也仅有1万亿倍太阳质量。它们的距离均在110亿光年之外。     

仙女座β的“幽灵”

在可见光波段看来,这个名为NGC404的星系似乎只是一个白色斑点（上面左图的中间）。它完全被仙女座β星（奎宿九）的光芒所掩盖了。仙女座β是一颗红巨星,它的辐射主要集中在可见光波段,NGC404被它的厉芒淹没,被爱好者们戏称为“仙女座β的幽灵”。     

椭圆星系中的星系际尘埃

该文总结了近年来椭圆星系中尘埃起源研究中的一些关键问题,包括尘埃大小的分布及其组成、椭圆星系恒星质量损失速率、尘埃的两种加热机制(恒星辐射加热和电子-尘埃碰撞加热),以及由此导致的尘埃温度分布;尘埃的总质量估算;由热离子导致的尘埃破坏速率,以及与此相关联的椭圆星系热气体分布,等等.综合考虑这些因素,作者认为热气体分布对于椭圆星系中尘埃存在和破坏的影响不可忽视,椭圆星系中星系内部恒星质量损失产生尘埃的起源可能占据着非常重要的地位.     

Correlated Radio-Optical Variations on Intraday Timescales

Correlated radio-optical variations on intraday timescales have been observed (e.g. In BLO 0716 714) and such radio intraday variability is suggested to have an intrinsic ori- gin. Recently, multi-wavelength observations, simultaneous at radio, mm-submm, optical and hard X-rays, of 0716 714, show that during a period of intraday/interday variations at ra- dio and mm wavelengths, the apparent brightness temperature of the source exceeded the Compton-limit (～1012 K) by 2--4 orders of magnitude, but no Compton catastrophe (or no high luminosity of inverse-Compton radiation) was detected. It is also found that the intra- day/interday variations at mm-submm wavelengths are consistent with the evolutionary be- havior of a standard synchrotron source and for the intraday/interday variations at centimeter wavelengths opacity effects can play a significant role, which is consistent with the interpreta- tion suggested previously by Qian et al. Thus the apparent high brightness temperatures may probably be explained in terms of Doppler boosting effects due to bulk relativistic motion of the source. We will argue a scenario to simulate the correlations between the radio and optical variations on intraday timescales observed in BLO 0716 714 in terms of a relativistic shock propagating through a jet with a dual structure.     

Detection of CO Outflow in Rotating Cores

We investigate the effect of bulk motion on the detection of molecular outflows in the sources S 146, GGD27, and IRAS 22566 5830. The traditional techniques do allow for bulk motions or systematic VLSR shifts of the core emissions, which may cause contamination of the high velocity gas emissions, and outflows may either fail to be detected or have their properties miscalculated. We used a program to follow the systematic shift of VLSR and better results have been obtained.     

Feedback of Active Galactic Nuclei in Seyfert 2 Galaxies

It is well accepted that feedback from active galactic nuclei (AGNs) plays an important role in the coevolution of the supermassive black hole (SMBH) and its host galaxy,but the concrete mechanism of feedback remains unclear.A considerable body of evidence suggests that AGN feedback suppresses star formation in the host galaxy.We assemble a sample of Seyfert 2 galaxies with recent observational data of compact nuclear starbursts and estimate the gas surface density as a function of column density to illuminate the relation between feedback and AGN properties.Although there are some uncertainties,our data still imply the deviation from the star formation law (Kennicutt-Schmidt law).Further,they indicate that:(1) Feedback correlates with the Eddington ratio,rather than with the mass of SMBH,as a result of decreasing star formation efficiency.(2) The SMBH and the torus are probably undergoing coevolution.Conclusions presented here can be refined through future high resolution CO or HCN observations.     

The Effect of AGN and SNe Feedback on Star Formation, Reionization and the Near Infrared Background

Feedback from supernovae (SNe) and from active galactic nuclei (AGN) accom-panies the history of star formation and galaxy evolution. We present an analytic model to explain how and when the SNe and AGN exert their feedback effects on the star formation and galaxy evolution processes. By using SNe and AGN kinetic feedback mechanisms based on the Lambda Cold Dark Matter (LCDM) model, we explore how these feedback mecha-nisms affect the star formation history (SFH), the Near-Infrared Background (NIRB) flux and the cosmological reionization. We find the values of the feedback strengths, ∈AGN =1.0+0.50.3and ∈SN=0.04+0.02-0.02, can provide a reasonable explanation of most of the observational re-suits, and that the AGN feedback effect on star formation history is quite different from the SNe feedback at high redshifts. Our conclusions manifest quantitatively that these feedback effects decrease star formation rate density (SFRD) and the NIRB flux (in 1.4 - 4.0μm), and postpone the time of completion of the cosmological reionization.