Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies

The sizes of the Broad Line Region (BLR) of some Seyfert 1 galax-ies and nearby quasars can be determined by the reverberation mapping method.Combining with the observed FWHM of Hβ emission line and assuming that themotion of BLR clouds is virialized, the black hole masses of these objects have beenestimated. However, this method strongly depends on the poorly-understood geom-etry and inclination of the BLR. On the other hand, a tight correlation between theblack hole mass and the bulge velocity dispersion was recently found for both activeand nearby inactive galaxies. This may provide another method, independent of theBLR geometry, for estimating the black hole mass. Using this method for estimatingthe black hole mass and combining with the measured BLR size and FWHM of Hβemission line, we derived the BLR inclination angles for 20 Seyfert I galaxies underthe assumption that the BLR is disk-like. The derived inclination angles agree wellwith those derived previously by fitting the UV continuum and Hβ emission lineprofiles. Adopting a relation between the FWHMs of [OⅢ]λ5007 forbidden line andthe stellar velocity dispersion, we also estimated the BLR inclinations for 50 nar-row line Seyfert 1 galaxies (NLSls). We found that the inclinations of broad LineSeyfert 1 galaxies (BLS1s) are systematically greater than those of NLS1s, whichseldom exceed 30. This may be an important factor that leads to the differencesbetween NLS1s and BLS1s if the BLR of NLS1s is really disk-like.     

Properties of Broad Band Continuum of Narrow Line Seyfert 1 Galaxies

We have performed a statistical study of the properties of the broadband continuum of Narrow Line Seyfert 1 galaxies (NLS1s) by collecting ratio,infrared, optical and X-ray continuum data from various databases and comparedthe results with control samples of Broad Line Seyfert 1 galaxies (BLSls). We findthat the fraction (～ 6%) of Radio Loud (RL) NLSls is significantly less than thatof BLS1s (～ 13%), which is caused by the lack of radio-very-loud sources in theformer. The rarity of RL NLS1s, especially radio-very-loud ones, is consistent withthe scenario of small black hole and high accretion rate for NLSls. Six new radio loudNLSls are found and five RL NLS1 candidates are presented. In comparison withthe BLS1s, the NLS1s tend to have stronger far infrared emission, cooler infraredcolors and redder B- K color, which suggests that NLS1s are hosted by dust-richernuclei. The NLS1s also show steeper soft X-ray spectrum and large soft X-rayto optical flux ratio, while a significant fraction show fiat soft X-ray spectra. Atleast two factors can account for this, absorption and spectral variability. We alsoperform a correlation analysis between various broad band data. It is found thatmost correlations identified for NLS1s are also valid for radio quiet BLS1s: (1) theoptical colors are anti-correlated with X-ray spectral index; (2) higher optical, X-ray and NIR luminosity objects show bluer optical colors and red H - K color; (3)higher luminosity objects show warmer IRAS color; (4) the radio loudness correlateswith B - K and X-ray to optical flux ratio. Radio loud objects behave somewhatdifferently in a few correlations.     

Enhanced Star Formation in Seyfert 2 Galaxies

In this paper, we report our preliminary results on enhanced star formation activity in Seyfert 2 galaxies. By re-analysing the Tully-Fisher relation for Whittle's (1992) sample and for a Seyfert 2s' sample selecting from Veron-Cetty and Veron (1996), we find that (1) almost all Seyfert 2 galaxies with circumnuclear star formation have a ratio of far infrared (FIR) to blue luminosities (L_FIR/L_B) to be larger than 1/3; (2) for Seyfert 2 galaxies with L_FIR/L_B > 1/3, the Tuly-Fisher relation is similar to that of the normal spiral galaxies; while for those with L_FIR/L_B ≥ 1/3, they are significantly different from the normal ones, which confirms Whittle's suggestion of enhanced star formation activities in the circumnuclear regions of these Seyfert 2 galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relations between the IR-UV-X-ray Continuum and Emission Lines for a Large Composite Sample of Narrow Line and Normal Seyfert 1 Galaxies

1 INTRODUCTIONThe broad emission lines, the most important characteristics of active galactic nuclei (AGN),are generally believed to be emitted by photoionized gas in the clouds that are illuminated bythe UV to X-ray continuum radiation of the celltral source (Netzer 1990). The photoionizationmodel is quite successful in explaining the average emission line properties of AGNs using anaverage ionizing continuum. To date, there are two sets of statistical relationships between thecolltin…     

赛弗特星系中的分子环

介绍了近年来Ｓｅｙｆｅｒｔ领域中关于分子环（ｔｏｒｕｓ）研究情况和现状。分子环模型的提出源于２型Ｓｅｙｆｅｒｔ星系核的光学偏振观测的结果与传统的１型Ｓｅｙｆｅｒｔ核的观测特征的相似性。在ｔｏｒｕｓ结构存在的假设下,讨论其对观测的作用,阐述了ｔｏｒｕｓ可能的结构和演化及其在Ｓｅｙｆｅｒｔ统一模型中的重要地位。还讨论了ｔｏｒｕｓ的遮挡、束流效应和由此造成的多波段观测特性,着重介绍了散射效应及其造成的偏     

窄线Seyfert 1型星系研究的新进展

窄线Seyfert1型星系（NLS1）作为活动星系核的一个小类，由于其X射线等高能波段上独特的观测特征，近年来越来越受到天文学界的广泛关注，详细描述了NLS1在观测及理论上的一些新进展，并对其主要模型作了较细致的讨论。     

Luminosity Functions of Quasars and Seyfert Galaxies

The optical luminosities of extragalactic objects with broad emission lines, i.e. quasi-stellar radio sources, radio quiet quasi-stellar objects and Seyfert galaxies are compared. At high luminosities (M < - 23) we find no difference in the form of the optical luminosity function for radio quiet and radio emitting objects; at low luminosities this function is growing steeply only for radio quiet objects, whereas for objects with higher radio indices it remains nearly constant below M = - 22. This may possibly be interpreted as indicating a division between the optically bright “quasars” and the less luminous objects. The quasars with the highest radio index show only a small scatter in optical luminosities and thus yield a well defined Hubble relation.     

Kinematics and Stellar Populations of Seyfert Galaxies

We have analyzed high signal-to-noise spectra of 10 active galaxies in order to investigate the stellar populations of these objects and the kinematics of the gas and stars in their nuclei. This revised version was published online in July 2006 with corrections to the Cover Date.     

二个新观测到的红外选赛弗特星系

根据２５μｍ和６０μｍ间的红外谱指数及６０μｍ和１００μｍ的相对流量选择了６个天体，在１９９４年９月９日至１１日期间，利用北京天文台２．１６ｍ望远镜观测了它们的光谱。经处理后，发现了一个新的Ｓｅｙｆｅｒｔ２和一个Ｓｅｙｆｅｒｔ３星系，另外还有一个ＨＩＩ星系。     

Seyfert 2型星系中的星暴活动

星暴和活动星系核之间的联系是活动星系研究领域最重要、最活跃的研究课题之一。Seyfert星系由于距离较近、数目较多和相对低的核活动,已成为研究星暴和活动星系核之间联系的理想天体。综述了活动星系核中存在星暴的观测证据和Seyflert2型星系核区星暴活动的最新研究结果,着重讨论了存在两类Seyflert2型星系(一类是被遮挡的Seyfert1型星系,另一类是“真正”的Seyfert2型星系即不存在宽线区的Seyfert2型星系)的可能性．通过比较具有和不具有偏振宽线的Seyflert2型星系在红外、射电、光学和X射线光谱性质的差别,发现具有偏振宽线的Seyfert2型星系在本质上和Seyflert1型星系是同一类天体,差别只在于观测者视线方向的不同;而不具有偏振宽线的Seyfert2型星系是一些星系核活动较弱而星暴活动占主导的天体,这些星系从射电、红外、光学到硬X射线,都具有和星暴星系相似的性质。由于这些星系中核的吸积率将比Seyflert1型星系低近两个量级,因而它们很有可能是一些没有宽发射线区的Seyfert2型星系,即所谓的“真正”Seyflert2型星系。     

赛弗特星系恒星速度弥散度的测量

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.     

Rapid X-Ray Variability of Seyfert 1 Galaxies

The rapid and seemingly random fluctuations in X-ray luminosity of Seyfert galaxies provided early support for the standard model in which Seyferts are powered by a supermassive black hole fed from an accretion disc. However, since EXOSAT there has been little opportunity to advance our understanding of the most rapid X-ray variability. Observations with XMM-Newton have changed this. We discuss some recent results obtained from XMM-Newton observations of Seyfert 1 galaxies. Particular attention will be given to the remarkable similarity found between the timing properties of Seyferts and black hole X-ray binaries, including the power spectrum and the cross spectrum (time delays and coherence), and their implications for the physical processes at work in Seyferts.     

Integral Field Spectroscopy of Six Seyfert Galaxies

We summarize the main conclusions derived from integral field spectroscopy, with optical fibres, of six Seyfert galaxies. More than 95 spectra around the active nucleus have been obtained showing asymmetric emission-line profiles at different positions. Continuum and emission-line intensity maps and ionized gas velocity fields have been derived for these six galaxies. We also present the stellar velocity field for NGC 1068, NGC 3516 and NGC 985. This revised version was published online in July 2006 with corrections to the Cover Date.     

Narrow-band Emission-Line and Continuum Images of Seyfert Galaxies

We present narrow-band emission line (Hα + [N II]λλ 6548, 6583, [O III] λλ 4959, 5007)as well as green or red continuum images of selected Seyfert galaxies. The sample includes NGC 7214, IC 4218, Akn 479, Mrk 915, IC 1515 and F 348. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Variability of Hardness Ratio 1 observed by ROSAT： Narrow—Line Seyfert 1 Galaxies versus Broad—Line Seyfert 1 Galaxies

We examined the correlation between the ROSAT Hardness Ratio 1 and Count Rates eight Narrow-line Seyfert 1 Galaxies (NLS1s) and 14 Broad-line Seyfert 1 Galaxies (BLS1s). We found that six of the NLS1s show a positive HR1-CTs correlation, and seven of the BLS1s, a negative correlation. The other two NLS1s and seven BLS1s do not show any clear HR1-CTs correlation. Thus, the spectral behavior is statistically different for the NLS1s and BLS1s. The different behaviors can possibly be interpreted in terms of a stable ‘soft excess’ that is strong in NLS1s and weak in BLS1s, plus a power law component, common to both, which softens with increasing flux.     

Relationship between Infrared and Radio Emission of Seyfert Galaxies

The relationships between the monochromatic luminosity of Seyfert galaxies at frequencies of 0.408, 1.49, and 4.85 GHz and the integrated luminosity in the far infrared (IR) range are investigated. At all radio frequencies they are linear and equally close. Some Seyfert galaxies, of morphological types S0/a, E, and S0, have a far higher radio luminosity than Seyfert spiral galaxies with the same IR luminosity. Most of them are found to have compact central radio components. Seyfert spiral galaxies follow the same relationship between radio and IR emission as non-Seyfert spiral galaxies. The relationships between radio and IR luminosity for the individual groups of galaxies of spectral types Sy 1-Sy 1.5 and Sy 1.8-Sy 2 are also linear.     

Broad-Band Radio to X-Ray Properties of Seyfert Galaxies

We report on the statistical analysis of a sample of AGNs (Seyferts and LINERs) selected from an RBSC-NVSS sample of the brightest X-ray sources. The sample is large enough and unbiased for a detailed study of multi-frequency (radio to X-ray) properties of AGN. There are no significant differences in X-ray, optical, far-infrared, and radio powers, core dominance, radio loudness, radio spectral index, and two-point radio-to-optical and optical-to-X-ray spectral indices of Seyfert types 1 and 2. These findings strongly support the unification model, and the observed differences between Sy1 and Sy2 are due to both the variable obscuration and different geometric orientation effects. The correlation between the X-ray and radio emission over many decades is primary and indicates the intrinsically similar origin of both radiations in Seyfert galaxies, powered mainly by AGN, rather than compact starbursts. For Seyfert galaxies we found that the slopes of the relations L _X - L _R and L _X - L _B are flat, which indicate the existence of components unrelated with X-ray. Perhaps only for LINERs is the observed L _X - L _R relation completely due to AGNs. The Sy1, Sy2, and LINER galaxies show different slopes in the relation L _X - L _1.4, and the relative contribution of extended radio components may be the cause of these differences. The possible effects of unresolved extended radio and X-ray components are quantitatively discussed.     

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.     

Molecular Cloud Formation in Disk Galaxies: The Case of M33

We present results from the BIMA survey of ¹²CO(1→0)emission from M33. The survey resolves this emission into individualobjects making this study the first unbiased, complete census of giantmolecular clouds (GMCs) in a spiral galaxy. The GMCs are clearlyassociated with dense atomic gas, suggesting formation from the HI. Moreover, high resolution observations of these clouds show thatthey appear the same as Milky Way GMCs when viewed through the sameobservational filters. The GMCs show significantly less angularmomentum than predicted by simple formation theories, suggesting theimportance of magnetohydrodynamic effects in their formation.