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1.
本文简要介绍了在活动星系核 (Seyfert星系 )统一模型研究领域的研究结果。最近的研究结果表明Seyfert1和 2型星系的差别不仅仅是视线方向上的不同 ,星系的环境、演化、星系核的活动等在活动星系核的统一模型中都起着非常重要的作用。最新的观测和理论研究发现Seyfert 2型星系中宽线区存在和星系核的活动密切相关。在一些核活动较低的Seyfert 2型星系中 ,宽线区很可能不存在 ,即可能存在所谓的“真正”的Seyfert 2型星系。 相似文献
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星暴星系是一类内部正在发生极为剧烈恒星形成的天体。介绍了星暴星系的研究历史及星暴星系的定义。综述了从射电波段到Ｘ射线波段星暴星系的光度光谱观察特征及其研究的最新进展。列出了星暴星系研究中存在的一些热点问题,包括星暴的触发机制,星暴时标,星族组分,恒星形成率,内红化以及星暴星系与活动星系核之间的关系等。最后,简述了可能有助于解决这些问题的观测手和理论方法。 相似文献
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本文收集了射电源表１Ｊｙ,Ｓ４ ,Ｓ５ 中的活动星系核的宽发射线数据,发现射电活动星系核的宽发射线与５ＧＨｚ 射电辐射强相关。ＢＬＬａｃ 天体具有较弱的宽发射线辐射,但具有与其它活动星系核类似的统计行为。结果表明射电活动星系核中的喷流与吸积过程存在本质联系。 相似文献
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活动星系核（AGN）是宇宙中最奇特的天体之一。它是真正意义上的全波天体，其中X射线波段的发射功率占到全波段功率的50％左右。AGN的X射线辐射研究涉及天体物理中的最基本问题，例如能量产生、辐射机制和宇宙论等，而Chandra X射线卫星的高分辨率图像和光谱对这一研究有着重要作用。以Chandra卫星的部分观测结果为例，简要介绍了几类不同类型AGN的X射线辐射研究进展：（1）宽吸收线类星体APM08279＋5255（z=3．91）的X射线谱分析，以及高红移类星体的观测概况；（2）Seyfert星系NGC 4151延展X射线发射问题的解决，及NGC 1068X射线辐射与光学波段的高激发态发射线（[OⅢ]λ5007）有很强相关性的发现；（3）6个BLLac天体样本的X射线环境分析；（4）射电星系X射线喷流的观测等。 相似文献
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通过搜集了457个活动星系核样本,根据活动星系核的演化实质是指宇宙时标上的变化,讨论了红移量与活动星系核演化的关系,最终证明了活动星系核的演化分为两个序列:(1)从类星体到Seyfert星系之间的演化;(2)平谱射电类星体(FSRQ)—BL Lac天体—射电星系(RG)的演化。 相似文献
8.
本文发表的是用北京天文台60厘米施密特望远镜进行发射线星系物端棱镜巡天结果的第四篇文章。文中的表1包括100个发射线天体,其中的96个是发射线星系;其余的对象有3个行星状星云,1个发射线星。在这些发射线星系中,属于s,sd型的有69个,d,ds型的有27个,分别占72％和28％。除了4个已知的Seyfert星系之外,至少还有5个也可能是Seyfert星系。这些发射线天体中的23个是IRAS源,它们都与具有强发射的现象相联系. 相似文献
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随着探测设备角分辨率和灵敏度的提高,喷流、喷流节点和热斑等活动星系核延展结构在射电、红外、光学、X射线等越来越多的波段被探测到,分辨出其更细致的结构,促进了理论研究热潮的兴起,使该领域成为当今天体物理研究的活跃领域之一。喷流是由活动星系核中心产生的准直等离子体外流,由中心黑洞驱动。至今,对喷流的成分、产生、准直原理和加速机制等基本问题并不清楚。另一方面,对于喷流、喷流节点和热斑等活动星系核延展区的辐射机制,一般认为其射电和光学辐射由相对论电子的同步辐射产生,但X射线的起源就存在着一定的争议。简单概述该领域近年来观测和理论研究进展。 相似文献
10.
BL Lac型天体是一类特殊的活动星系核,根据辐射能谱的不同可以分为低峰值频率BL Lac型天体(LBLs),中间峰值频率BL Lac型天体(IBLs),高峰值频率BL Lac型天体(HBLs),以及极高峰值频率BL Lac型天体(UHBLs)。不同类型BL Lac型天体具有不同的辐射特性,通过射电、光学、X射线、伽玛射线等多波段的观测可以发现很多特殊类型及辐射特性的BL Lac型天体,而甚长干涉测量技术(Very Long Baseline Interferometry,VLBI)是目前分辨率最高的观测技术,也是探测致密核区结构的唯一手段。主要介绍目前对BL Lac型天体的VLBI观测研究概况,以及对其中一些特殊BL Lac型天体VLBI研究的进展及初步结果。 相似文献
11.
Andy Thean Alan Pedlar Marek J. Kukula Stefi A. Baum Christopher P. O'Dea 《Monthly notices of the Royal Astronomical Society》2001,325(2):737-760
We discuss the properties of compact nuclear radio components in Seyfert galaxies from the extended 12-μm AGN sample of Rush et al. Our main results can be summarized as follows.
Type 1 and type 2 Seyferts produce compact radio components which are indistinguishable in strength and aspect, indicating that their central engines are alike, as proposed by the unification model. Infrared IRAS fluxes are more closely correlated with low-resolution radio fluxes than high-resolution radio fluxes, suggesting that they are dominated by kiloparsec-scale, extranuclear emission regions; extranuclear emission may be stronger in type 2 Seyferts. Early-type Seyfert galaxies tend to have stronger nuclear radio emission than late-type Seyfert galaxies. V-shaped extended emission-line regions, indicative of 'ionization cones', are usually found in sources with large, collimated radio outflows. Hidden broad lines are most likely to be found in sources with powerful nuclear radio sources. Type 1 and type 2 Seyferts selected by their IRAS 12-μm flux densities have well-matched properties. 相似文献
Type 1 and type 2 Seyferts produce compact radio components which are indistinguishable in strength and aspect, indicating that their central engines are alike, as proposed by the unification model. Infrared IRAS fluxes are more closely correlated with low-resolution radio fluxes than high-resolution radio fluxes, suggesting that they are dominated by kiloparsec-scale, extranuclear emission regions; extranuclear emission may be stronger in type 2 Seyferts. Early-type Seyfert galaxies tend to have stronger nuclear radio emission than late-type Seyfert galaxies. V-shaped extended emission-line regions, indicative of 'ionization cones', are usually found in sources with large, collimated radio outflows. Hidden broad lines are most likely to be found in sources with powerful nuclear radio sources. Type 1 and type 2 Seyferts selected by their IRAS 12-μm flux densities have well-matched properties. 相似文献
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A number of studies have shown that the visibility of scattered broad emission lines in Seyfert 2 galaxies is strongly dependent on the IRAS flux ratio, where those Seyfert 2 galaxies with 'warm' IRAS colours show polarized broad line emission. It is now clear that this effect is owing to the increasing dominance of the galactic rather than the active galactic nucleus (AGN) emission at 60 μm in less-luminous 'cool' Seyfert 2 galaxies. However, we present evidence that the 25-μm emission is a good measure of the AGN luminosity for most Seyfert 2 galaxies. Using this result, we show that the visibility of scattered broad line emission has a dependence on the AGN luminosity. The observations can be interpreted self-consistently if the scaleheight of the scattering zone varies with central source luminosity whilst the scaleheight of the obscuring torus is approximately constant. 相似文献
13.
Veeresh Singh Prajval Shastri Ramana Athreya 《Journal of Astrophysics and Astronomy》2011,32(4):497-500
Seyfert galaxies are classified mainly into type 1 and type 2 depending on the presence and absence of broad permitted emission
lines in their optical spectra, respectively. Unification scheme hypothesizes that the observed similarities and differences
between the two Seyfert subtypes can be understood as due to the differing orientations of anisotropically distributed obscuring
material having a torus-like geometry around the AGN. We investigate the radio continuum emission properties of a sample of
Seyfert galaxies in the framework of the unification scheme. 相似文献
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The unified model for Seyfert 2s postulates that these galaxies are in fact normal Seyfert ls whose innermost regions are hidden from a direct view by an opaque torus. Galaxies seen from a line-of-sight within the opening angle of this torus have the central continuum source and the Broad Line Region unobstructed, and are classified as Seyfert 1/QSO. In Seyfert 2s, on the other hand, periscopic views of the hidden nucleus may be obtained through scattering of the nuclear light in the extranuclear regions. If this model is correct, the Blue and Featureless Continuum observed in many Seyfert 2s is simply a mirror image of the obscured nucleus. In this case, the light from the Broad Line Region must also be reflected towards the observer. Seyfert 2s should therefore exhibit broad lines in their spectrum, which, by definition, they do not! In this contribution we examine this issue and the complications it brings to the basic unification picture of Seyfert galaxies. We fail to find a consistent explanation for this question in the framework of the unified model. An alternative modified-unified model for Seyfert 2s is proposed. 相似文献
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We present data from the Infrared Space Observatory (ISO) of a complete set of Seyfert galaxies (Seyfert 1 and Seyfert 2)
in a wavelength range seldom explored so far. These data allow a detailed study of the far IR Spectral Energy Distribution
of these sources.
A Bayesian inversion method has been used to invert the Spectral energy Distribution (SED) of these sources yielding two fundamental
results, namely that the far IR SED of Seyfert Galaxies can be explained solely through thermal reradiation of high energy
photons by dust. And, that this thermal emission is made up of two or three independent components.
Comparisons between the parameters obtained from the analysis of the IR SEDs and the emission in other wavelengths ranges
(radio and X-rays) show that the host galaxies are key elements in the understanding of the IR emission of Seyferts. Besides,
the nuclear properties seem to be adequately explained with the Unified Models of AGN, that state that the differences seen
between the broad (Seyfert 1) and narrow (Seyfert 2) line objects are due to geometrical orientation effects.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimet- ric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines (PBLs) are absorbed by NH < 1024 cm-2, while two of three Seyfert 2 galaxies without PBLs show evidence of Compton-thick obscuration, support- ing the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs. Adding the measured obscuration indicators (NH, T ratio, and Fe Kα line EW) of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for NH, 99.1% to 99.4% for T ratio, and 95.3% to 97.4% for Fe Kα line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angles of the line of sight to the putative dusty torus, which leads to the obscuration of the broad-line scattering screen, as expected in the unification model. 相似文献
17.
Conclusions Since there is sufficiently detailed information on the observed galaxies listed in the notes to Table 1, we briefly summarize the main results.From the observations of 94 objects, emission lines are discovered in 64; in one, Markaryan 396, hydrogen absorption lines are observed (this is a white dwarf, probably type DA, and possibly a weak radio source [23]). In the red region there are no lines detected in the objects Markaryan 422(3), 425(3), 431(4), 433(3), 616(3), 621(5), 643(4), 655(5), 656(4), and 658(3); the number of spectrograms is indicated in parentheses; it is possible that Markaryan 643 is a galactic cluster.The objects Markaryan 595, 609, 622, 688, 699, and 700 have broad, hydrogen emission lines and can be attributed to the Seyfert class of galaxies. Markaryan 609, 622, and 699, plus, probably, Markaryan 423, possess moderate Seyfert characteristics. Furthermore, in Markaryan 414, 584, 612, 617, 646, 670, 684, and 693 broad emission lines are observed or suspected. Markaryan 586 is probably similar to a QSO. Further observations are advisable for all these objects.In conclusion, the authors express their gratitude to A. L. Shcherbanovskii for help in the treatment of the spectrograms on the M-222 computer.Institute of Astrophysics, Academy of Sciences of the Kazakh SSR. Special Astrophysical Observatory, Academy of Sciences of the USSR. Translated from Astrofizika, Vol. 12, No. 4, pp. 665–682, October–December, 1976. 相似文献
18.
Ying-He Zhao Qiu-Sheng Gu Zhi-Xin Peng Lei Shi Xin-Lian Luo Qiu-He Peng Department of Astronomy Nanjing University Nanjing 《中国天文和天体物理学报》2006,6(1):15-24
As part of a study of star formation history along the Hubble sequence, we present here the results for 11 elliptical galaxies with strong nebular emission lines.After removing the dilution from the underlying old stellar populations by use of stellar population synthesis model,we derive the accurate fluxes of all the emission lines in these objects,which are then classified,using emission line ratios, into one Seyfert 2,six LINERs and four HII galaxies.We also identify one HII galaxy (A1216 04)as a hitherto unknown Wolf-Rayet galaxy from the presence of the Wolf- Rayet broad bump at 4650 (?).We propose that the star-forming activities in elliptical galaxies are triggered by either galaxy-galaxy interaction or the merging of a small satellite/a massive star cluster,as has been suggested by recent numerical simulations. 相似文献
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星系中心黑洞质量和核球恒星速度弥散度的紧密关系揭示出准确测量恒星速度弥散度对测定星系中心黑洞质量尤为重要.文中提供了一种利用SDSS(Sloan Digital SkySurvey)光谱测定速度弥散度及其不确定性的方法.通过对像素空间包含显著特征吸收线的4个不同谱区的拟合,得到准确测量恒星速度弥散度σ的光谱区域.文中4个拟合波段主要包含的吸收线为CaⅡK,MgⅠb三重线(波长5167.5,5172.7,5183.6(?))和CaT(CaⅡ三重线,波长8498.0,8542.1,8662.1(?)).不同区域结果表明,MgⅠb区由于受到铁族发射线影响,拟合的σ值偏低;CaⅡK线区谱线强度很弱,易受限于最小二乘法搜索算法;CaT+CaⅡK联合区得出的速度弥散度和只计算CaT区域的结果相当.利用该方法,测试了一个红移小于0.05的赛弗特星系样本,发现CaT区是测速度弥散度的最佳谱区. 相似文献
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J. P. Halpern T. J. Turner I. M. George 《Monthly notices of the Royal Astronomical Society》1999,307(4):L47-L50
The X-ray source AXJ0341.4–4453 was described by Boyle et al. as a Type 2 active galactic nucleus (AGN) at z =0.672 based on the absence of broad emission lines in the observed wavelength range 4000–7000 Å. We obtained a new spectrum of AXJ0341.4–4453 extending to 9600 Å which reveals broad Balmer lines and other characteristics of Seyfert 1 galaxies. The FWHM of broad H β is at least 1600 km s−1 , while [O iii ] λ 5007 has FWHM=730 km s−1 . The flux ratio [O iii ] λ 5007/H β =1. Thus, AXJ0341.4–4453 is by definition a narrow-line Seyfert 1 galaxy, or perhaps a moderately reddened Seyfert 1 galaxy, but it is not a Type 2 QSO. Although examples of the latter have long been sought, particularly in connection with the problem of the X-ray background, there is still virtually no evidence for the existence of any Type 2 QSO among X-ray selected samples. 相似文献