VLBI总体条纹拟合方法的应用及其效果

用总体条纹拟合求解各天线的延迟量和条纹率参数,可以提高与小天线相关基线的灵敏度。本文以射电致密陡谱源(CSS)3C43为例,就如何提高数据的信噪比,尽可能多地保留有效数据方面做了成功的尝试.从而十分有效地使用了总体条纹拟合方法.我们认为:对源结构的预知,配以恰当的处理技巧,能获取更多射电源结构信息,改善成图质量.     

致密陡谱源3C43、3C48和3C454的VLBI研究

利用美国甚长基线阵对3个致密陡谱源3C43、3C48和3C454进行中心频率1.6GHz的观测,获得总流量图和各个子源的结构等信息.对比已有的数据,分析源3C43和3C454的流量变化和各个子源的位置移动,发现3C43的总流量、各子源流量、各子源的相对位置在14年内比较稳定;3C454的总流量和各子源流量也比较稳定,但两个子源相对核心的偏离速度分别是光速的21.6和17.7倍,存在明显的视超光速现象.同时通过对L波段4个频率的总流量结果进行谱指数拟合,获得源3C43和3C454的谱指数分别是0.63和0.86,符合致密陡谱源谱指数α≥0.5的定义,也与已有的结果吻合较好.     

未证认的IRAS LRS源的光学证认和观测研究——1.北天O~h—12~h具有硅酸盐特征的源

本文给出了IRAS LRS表中0°<δ<66°0~h<α<12~h的未被证认的2n、3n类源的光学证认图、近红外测光及近红外位置,并应用近红外和远红外双色图对观测结果进行了定性分析.结果表明:其中大部分源是AGB或RGB星,但还有几个特殊的源,我们分别对它们进行了讨论.     

两颗致密射电源的327MHz VLBI观测

1989年6月，对两颗射电源（3C345和3C454.3）作了327MHz VLBI观测。本文给出两颗源的模型拟合参数，并就结构作了分析和讨论。VLBI数据的相关处理和分析是在上海天文台VLBI系统上完成的。     

致密陡谱源1150+497(4C49.22)的射电研究

利用美国甚长基线阵,在5GHz和8GHz波段观测致密陡谱源(CSS)1150+497,获得的5GHz总流量图显示1150+497有单边喷流结构。在5GHz波段该源的西南方向探测到3个亮结,在东北方向探测到一个亮结。在8GHz波段该源的西南方向探测到2个亮结。在5GHz波段,根据子源A和E自1982~2001年间3个时段的VLBI观测成图结果,拟合出它们的分离速度为0.478±0.007mas/year。     

高红移耀变体4C 38.41光学多波段光变性质

4C 38.41是一颗红移为1.813、可分类为平谱射电类星体的耀变体,使用一台85 cm望远镜在2018年2月22日至26日期间对其进行了光学V和R波段测光观测,得到两个波段的准同时数据.基于这些数据分析了该源在不同光变时标下的光变特性.结果表明:这颗源在观测期间处于较弱的活动状态, V和R波段星等(V, R)总变化均约为0.20等.在天内时标下,其中3晚探测到了该源的天内光变,另有一晚可能存在天内光变.此外,通过色指数和时延分析发现4C 38.41在不同时标下都展现越亮越红行为,与大多数平谱射电类星体类似,但在最后一晚4C 38.41在颜色-星等图上呈现出v字形,即首先展现越亮越红行为,然后转变为越亮越蓝行为,这可能是由该源的辐射在吸积盘主导和喷流主导之间的转换造成的.此外在第2晚探测到了V、R波段之间的时延,这是首次在高红移耀变体中探测到不同光学波段光变之间的时延,可以用随机同步辐射小结构模型来解释.     

巨射电星系3C236的326.5MHz射电研究

用4km Ooty综合孔径射电望远镜,在326.5MHz频率上,对巨射电星系3C236进行了射电观测。该文给出了巨射电星系3C236在326.5MHz上的射电图,并作了简单的分析讨论,得到一些初步结果。     

大质量恒星形成核区的特性：^12CO、^13CO和C^18O的谱线观测及统计比较

利用青海站的13.7米射电望远镜对河内24个与水脉泽源成协并有红外Spitzer数据的巨分子云核进行12CO(J=1→0),13CO(J=1→0)和C18O(J=1→0)的同时成图观测,平均的成图范围为81×81.并全部探测到了C18O的谱线发射,其中11个源有较大范围(51-81)的C18O成图,这些分子云核均观测到C18O(J=1→0)谱线积分强度极大值的一半处,其余的13个源由于信噪比低或者成图范围较大等原因,没有进行如此大面积的成图观测.对样本中的11个已成图的稠密核进行了云核特性的分析并统计比较了CO与13CO,13CO与C18O及CO与C18O谱线积分强度之比(R12/13,R12/13,R12/18),结果是,C18O是光学薄的,可以探测到云核更加细致的结构.从核中心到边缘,3种谱线积分强度比是逐渐增加的.CO与13CO的谱线积分强度比R12/13的范围在2-6之间;13CO与C18O的比值R13/18范围在4-20之间波动,中心区域其值大部分集中在6-12之间,变化范围波动不是很大;CO与C18O之比R12/18在13-90更大的范围内,在更加致密的云核中心该比值集中在13-50之间.     

AST3图像相减测光模板系统设计

AST3是将要安装于位于南极内陆冰穹A的昆仑站的3台口径50 cm的施密特望远镜,寻找变源(尤其是瞬间变源)是其科考目标之一,需要通过图像相减测光方法实现.首先需要根据初期的观测数据生成标准模板图像,而后在长期观测过程中,将模板图像与新观测到的图像进行相减测光处理,从而发现变源.模板在观测中起着举足轻重的作用,给出了模板制作的流程,并且验证了其可实现性和功能的正确性.     

Cepheus OB3巨分子云复合体成块性质的研究

根据文[1]中图1（a）和图1（b），分别对CepB和CepF进行成图处理，得到了它们的强度分布图和速度分段积分等高图，通过对这些强度分布图和速度分段积分等高图的分析和研究，也得到了CegheusOB3巨分子云复合体是成块的，并且这些块是没有被自引力束缚的，同时还得到了CepB和CepF的外流的动力学时标。     

Superluminal motion in the parsec-scale jet in 3C 380

We present extensive multi-epoch VLBI observations of the quasar 3C 380 which reveal a bent parsec-scale radio jet with complex substructure which exhibits superluminal motion out to ∼100 pc from the active core. The general characteristics of the jet and its motion are similar to those in several other well-studied superluminal sources, most notably a rapid increase in the opening angle at a projected distance of a few tens of parsecs from the core and apparent acceleration along the jet. This acceleration could be a simple kinematic effect associated with bulk flow at a constant speed, but at a varying angle to the line of sight. The jet is well resolved in the transverse direction for the majority of its length and resembles numerical simulations of a jet disrupted by the rapid growth of sinusoidal 'Kelvin–Helmholtz' modes. Our maps also reveal extremely rapid localized variations in brightness which have not yet been seen in other nuclear jets. We suggest that phase effects, arising from the intersection of oblique shocks, may be the cause of these dramatic changes. 3C 380 is often classified as a compact steep spectrum (CSS) source; however, in contrast to the majority of CSS sources, it is likely that 3C 380 is simply a powerful FRII source seen approximately end-on.     

Compact radio sources variable at 151 MHz – II. High-resolution observations of an unbiased sample

High‐resolution observations, made with the Very Large Array (VLA) at 330 MHz, 1.4 GHz and 8.4 GHz and with the Ryle Telescope at 15 GHz, are presented of a sample of 23 sources which are variable at 151 MHz, concluding the observations of an unbiased sample of 40 such sources. The 8.4 GHz emission of almost all of the sources is dominated by structure on a scale ≲0.1 arcsec – the spectra of these compact components are such that they will also dominate the emission at 151 MHz; the number of sources for which this is not the case is consistent with the number of spurious variables expected to be found in the sample. About two-thirds of the sources have the self-absorbed, or flat, spectra expected from their size. The majority (∼75 per cent) of the sources belong to the compact steep-spectrum (CSS) class, but are generally more compact than other CSS sources; the CSS variables also appear to exhibit more spectral ageing than typical CSS sources, which may indicate a difference in the nature of the sources.     

Near-infrared spectroscopy of powerful compact steep-spectrum radio sources

We have obtained near-infrared spectroscopy of a small sample of powerful compact steep-spectrum (CSS) radio sources mainly, but not exclusively, from the 3CR sample. We find no differences between the distributions in the equivalent width and luminosity of the [O  iii ]λ5007 line for our sample and other larger, presumably older, high-redshift 3C objects, suggesting that the underlying quasar luminosity remains roughly constant as quasars age. We also find a possible broad line in 3C 241, adding to recent evidence for broad lines in some radio galaxies.     

Compact steep-spectrum sources from the S4 sample

We present the results of 5-GHz observations with the VLA A-array of a sample of candidate compact steep‐spectrum (CSS) sources selected from the S4 survey. We also estimate the symmetry parameters of high-luminosity CSS sources selected from different samples of radio sources, and compare these with the larger sources of similar luminosity to understand their evolution and the consistency of the CSS sources with the unified scheme for radio galaxies and quasars. The majority of CSS sources are likely to be young sources advancing outwards through a dense asymmetric environment. The radio properties of CSS sources are found to be consistent with the unified scheme, in which the axes of the quasars are observed close to the line of sight, while radio galaxies are observed close to the plane of the sky.     

VLA observations of hot spots in high luminosity radio sources

VLA observations at 6 cm have been made of 16 distant luminous 3C sources that appeared to be unresolved or slightly resolved in Cambridge maps but which were known from VLBI observations to contain significant fine structure on the scale of about 1 kpc in their lobes. The general morphology of these sources is very similar to that of their nearby powerful counterparts; most of the lobes contain low brightness tails which are often directed from the hot spots towards the associated optical object. The hot spots are generally unresolved by the VLA observations; in 3C 254, 3C 268.4 and 3C 352, one of the lobes contains two hot spots.     

A VLBI Study of Compact Steep Spectrum Sources 3C43, 3C48 and 3C454

We used the VLBA(NRAO, USA) and made VLBI observations towards the compact steep spectrum sources 3C43, 3C48 and 3C454 at the central frequency 1.6 GHz, and obtained their total flux density maps and information on the structures of their components. By comparison with the previous data, we analyzed the variations of their flux densities as well as the displacements of their components. It is found that the total flux density of the source 3C43, as well as the flux densities and relative positions of its components are quite stable in 14 years. For the source 3C454, the total flux density and the flux densities of its components are also relatively stable, but two of the components moved away from the central core with superluminal velocities of 21.6c and 17.7c. Fitted to their flux densities at 4 L-band frequencies, the spectral indexes of the sources 3C43 and 3C454 were obtained to be 0.63 and 0.86, respectively, in good agreement with previous results, and consistent with the definition of α ≥0.5 for compact steep spectrum sources.     

Compact stellar systems around NGC 1399

We have obtained spectroscopic redshifts of colour-selected point sources in four wide area VLT-FLAMES (Very Large Telescope-Fibre Large Array Multi Element Spectrograph) fields around the Fornax cluster giant elliptical galaxy NGC 1399, identifying as cluster members 27 previously unknown faint     compact stellar systems (CSS), and improving redshift accuracy for 23 previously catalogued CSS.
By amalgamating our results with CSS from previous 2dF observations and excluding CSS dynamically associated with prominent (non-dwarf) galaxies surrounding NGC 1399, we have isolated 80 'unbound' systems that are either part of NGC  1399's globular cluster (GC) system or intracluster GCs. For these unbound systems, we find (i) they are mostly located off the main stellar locus in colour–colour space; (ii) their projected distribution about NGC  1399 is anisotropic, following the Fornax cluster galaxy distribution, and there is weak evidence for group rotation about NGC  1399; (iii) their completeness-adjusted radial surface density profile has a slope similar to that of NGC  1399's inner GC system; (iv) their mean heliocentric recessional velocity is between that of NGC  1399's inner GCs and that of the surrounding dwarf galaxies, but their velocity dispersion is significantly lower; (v) bright CSS  ( M _V < −11)  are slightly redder than the fainter systems, suggesting they have higher metallicity; (vi) CSS show no significant trend in   g '− i '  colour index with radial distance from NGC  1399.     

Collimation of extragalactic radio jets in compact steep-spectrum and larger sources

We study the collimation of radio jets in the high-luminosity Fanaroff–Riley class II sources by examining the dependence of the sizes of hotspots and knots in the radio jets on the overall size of the objects for a sample of compact steep-spectrum (CSS) and larger-sized objects. The objects span a wide range in overall size from about 50 pc to nearly 1 Mpc. The mean size of the hotspots increases with the source size during the CSS phase, which is typically taken to be about 20 kpc, and the relationship flattens for the larger sources. The sizes of the knots in the compact as well as the larger sources are consistent with this trend. We discuss possible implications of these trends. We find that the hotspot closer to the nucleus or core component tends to be more compact for the most asymmetric objects where the ratio of separations of the hotspots from the nucleus r _d>2. These highly asymmetric sources are invariably CSS objects, and their location in the hotspot size ratio–separation ratio diagram is possibly the result of their evolution in an asymmetric environment. We also suggest that some sources, especially of lower luminosity, exhibit an asymmetry in the collimation of the oppositely directed radio jets.     

Solar brightness distribution and its variability at 3 millimeter wavelength

Solar mapping at 3.4 millimeter wavelength has shown the existence of various spatial structures in brightness distribution. The most prominent structure is presented by the local sources of the slowly varying component of the solar radio emission. Usually they coincide with active regions. Some sources have no corresponding optical counterparts. Using synoptic radio maps, latitudinal belts of enhanced brightness were detected at the north and south hemispheres. These belts seem to coincide with sunspot zones, but the enhanced emission exists independently of sunspot group appearance. Comparison of our maps with XUV images shows a noticeable resemblance. Sources above active regions and latitudinal belts of enhanced brightness are seen in both ranges as well as coronal holes.