Based on a new survey of AGN activity in Compact Groups of Galaxies, we report a remarkable deficiency of Broad Line AGNs as compared to Narrow Line AGNs. The cause of such deficiency could be related to the average low luminosity of AGNs in CGs: $10^{39}$ erg s$^{-1}$. This result may imply lower accretion rates in CG AGNs, making Broad Line Regions (BLR) undetectable, or may indicate a genuine absence of BLRs. Both phenomena are consistent with gas stripping through tidal interaction and dry mergers.
In this paper, results of optical identification of ASCA surveys are summarized. To understand luminous AGNs in the z<1 universe, the ASCA AGN sample is still better than samples of AGNs from deep Chandra or XMM-Newton surveys. Combining the identified sample of AGNs from ASCA Large Sky Survey and Medium Sensitivity Survey, the sample of hard X-ray selected AGNs have been expanded up to about 80 AGNs above the flux limit of 10^{-13} erg s^{-1} cm^{-2} in the 2-10keV band. One fifth of the ASCA AGNs are absorbed narrow-line AGNs. The luminosity distribution of the absorbed AGNs is limited below…
We have conducted a systematic search of AGNs with IMBHs from the SDSS DR4. As results we found 245 candidates of broad-line AGN with M_{BH}<10^6 \Msun estimated from the luminosity and width of the broad Halpha component. Compared to the pioneer Greene & Ho (2004) sample of 19 IMBH AGNs, our sample has improved in covering a larger range of the Eddington ratio, as well as black hole mass and redshift, taking the advantage of our AGN-galaxy spectral decomposition algorithm. Among these, thirty-six have L_{bol}/L_{Edd} < 0.1, hinting that a significant fraction of IMBHs might exist with weak or…
Type II AGNs with polarimetric broad emission line provided strong evidence for the orientation-based unified model for AGNs. We want to investigate whether the polarimetric broad emission line in type II AGNs can be used to calculate their central supermassive black hole (SMBH) masses, like that for type I AGNs. We collected 12 type II AGNs with polarimetric broad emission line width from the literatures, and calculated their central black hole masses from the polarimetric broad line width and the isotropic \oiii luminosity. We also calculate the mass from stellar velocity dispersion, $σ_*$, …
The Boltzmann-plot (BPT) method for laboratory plasma diagnostic was used for a quick estimate of physical conditions in the Broad Line Region (BLR) of 14 Active Galactic Nuclei (AGNs). For the BLR of nine AGNs, where PLTE exist, the estimated electron temperature are in the range T $\sim$ 130000K - 37000K are in good agreement with previous estimates. The estimated electron densities depend on the opacity of the emitting plasma in the BLR, and they are in range from $10^9\rm cm^{-3}$ (for optically thick plasma) to $10^{14}\rm cm^{-3}$ (for optically thin plasma). Although an alternative of P…
We present the results of a long-term variability campaign of very broad-line AGNs with line widths broader than FWHM $>$ 5000 kms$^{-1}$. The main goal of our investigation was to study whether the widths of the optical broad emission lines are correlated with the optical intensity variations on timescales of years. Our AGN sample consisted of 10 objects. We detected a significant correlation between optical continuum variability amplitudes and H$β$ emission line widths (FWHM) and, to a lesser degree, between H$β$ line intensity variations and H$β$ equivalent widths. We add the spectroscopic …
We present X-ray spectra of four ultraluminous infrared galaxies (ULIRGs) with detectable broad near-infrared emission lines produced by active galactic nuclei (AGNs): Mrk 463, PKS 1345+12, IRAS 05189-2524, and IRAS 07598+6508. With the exception of IRAS 07598+6508, high quality X-ray spectra obtained with XMM or Chandra show modest (30-340 eV) equivalent widths of the 6.4 keV Fe K alpha emission line and clear signatures for absorption at a level of 4-33 * 10^22 cm^-2 for the main power-law components from the AGNs. These spectral properties are typical of Compton-thin AGNs, and so we estimat…
(Abridged) Using an empirical relation between the broad line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 AGNs with double-peaked broad emission lines in two samples. With black hole masses from $3\times 10^7M_\odot$ to $5\times 10^9M_\odot$, these AGNs have the dimensionless accretion rates (Eddington ratios) between 0.001 and 0.1, and the bolometric luminosity between $10^{43}erg/s$ and $10^{46}erg/s$, both being significantly larger than those of several previously known low-luminosity double-peaked AGNs. The optical-X-ray spectr…
We present results of optical identification of the X-ray sources detected in the ASCA Large Sky Survey. Optical spectroscopic observations were done for 34 X-ray sources which were detected with the SIS in the 2-7 keV band above 3.5 sigma. The sources are identified with 30 AGNs, 2 clusters of galaxies, and 1 galactic star. Only 1 source is still unidentified. The flux limit of the sample corresponds to 1 x 10^{-13} erg s^{-1} cm^{-2} in the 2-10 keV band. Based on the sample, the paper discusses optical and X-ray spectral properties of the AGNs, contribution of the sources to the Cosmic X-ra…
We use a recently released SDSS catalog of X-ray emitting AGNs in conjunction with the FIRST 20cm radio survey to investigate the black hole fundamental plane relationship between the 1.4GHz radio luminosity ($L_r$), 0.1-2.4 keV X-ray luminosity ($L_X$), and the black hole mass ($M$), namely, $log L_r=ξ_{RX}log L_X+ξ_{RM}log M +const$. For this purpose, we have compiled a large sample of 725 broad-line AGNs, which consists of 498 radio-loud sources and 227 radio-quiet sources. Our results are generally consistent with those in our previous work based on a smaller sample of 115 SDSS AGNs. We co…
We present an investigation of the structure of the emission line region in a sample of 12 single-peaked Active Galactic Nuclei (AGNs). Using the high resolution H-beta and H-alpha line profiles observed with the Isaac Newton Telescope (La Palma) we study the substructure in the lines (such as shoulders or bumps) which can indicate a disk or disk-like emission in Broad Line Regions (BLRs). Applying Gaussian analysis we found that both kinds of emission regions, BLR and NLR, are complex. In this sample the narrow [OIII] lines are composites of two components; NLR1 which have random velocities f…
We identify active galactic nuclei (AGN) in the Groth-Westphal Survey Strip (GSS) using the independent and complementary selection techniques of optical spectroscopy and photometric variability. We discuss the X-ray properties of these AGN using Chandra/XMM data for this region. From a sample of 576 galaxies with high quality spectra we identify 31 galaxies with AGN signatures. Seven of these have broad emission lines (Type 1 AGNs). We also identify 26 galaxies displaying nuclear variability in HST WFPC2 images of the GSS separated by ~7 years. The primary overlap of the two selected AGN samp…
We assembled a sample of broad line and narrow lines AGNs observed by ASCA, whose excess variances have been determined. The central black hole masses in this sample can be obtained from the reverberation mapping method and the width of H$β$ emission line. Using the black hole masses and the bolometric luminosity, the Eddington ratio can also be obtained. We confirmed the strong anti-correlation between X-ray variability and the central black mass founded by Lu & Yu. We further found that narrow line Seyfert 1 galaxies (NLS1s) also follow this relation with a larger scatter and there is only a…
Velocity-resolved reverberation mapping suggests that the broad-line regions (BLRs) of AGNs can have significant net inflow. We use the STOKES radiative transfer code to show that electron and Rayleigh scattering off the BLR and torus naturally explains the blueshifted profiles of high-ionization lines and the ionization dependence of the blueshifts. This result is insensitive to the geometry of the scattering region. If correct, this model resolves the long-standing conflict between the absence of outflow implied by velocity-resolved reverberation mapping and the need for outflow if the blues…
The sizes of the broad-line regions (BLRs) in $γ$-ray active galactic nuclei (AGNs) are estimated from their optical continuum luminosity by using the empirical relation between $R_{\rm BLR}$ and $L_{λ,\rm opt}$. Using the broad emission line data, we derive the photon energy density in the relativistic blobs near the massive black holes in AGNs. We calculate the power of the broad-line photons Compton up-scattered by the relativistic electrons in the blobs. Compared with observed $γ$-ray emission data, the Doppler factors $δ$ of the blobs for a sample of 36 $γ$-ray AGNs are derived, which are…
We derived the black hole fundamental plane relationship among the 1.4GHz radio luminosity (L_r), 0.1-2.4keV X-ray luminosity (L_X), and black hole mass (M) from a uniform broad line SDSS AGN sample including both radio loud and radio quiet X-ray emitting sources. We found in our sample that the fundamental plane relation has a very weak dependence on the black hole mass, and a tight correlation also exists between the Eddington luminosity scaled X-ray and radio luminosities for the radio quiet subsample. Additionally, we noticed that the radio quiet and radio loud AGNs have different power-la…
We report the completion of a survey of radio-loud AGNs begun in an earlier paper, aimed finding and studying broad, double-peaked Balmer lines. We present Ha spectra of 13 broad-lined objects (3 with double-peaked Ha profiles). The final sample includes 106 radio-loud AGNs. 20% of the objects have Ha lines with double peaks or twin shoulders and of these, 60% can be fitted quite well with a model attributing the emission to a circular, relativistic, disk. We also compare the Hb and MgII profiles of 4 objects with models of photoionized accretion disks and find them to be in reasonable agreeme…
Although accretion disks are a theoretically appealing model for the geometry and dynamics of the gas in the vicinity of black holes in Active Galactic Nuclei (AGN), there is little direct observational evidence for their existence. The telltale signature of disk emission in AGN -- double peaked emission lines -- have so far been found in only two dozen cases in the optical. We have selected about 100 double-peaked broad emission line AGN from the Sloan Digital Sky Survey (SDSS) from a large sample of over 4000 AGN with z<0.4. By comparing the properties of these AGN with those of the full sam…
Using an eigenspectrum decomposition technique, we separate the host galaxy from the broad line active galactic nucleus (AGN) in a set of 4666 spectra from the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75. The decomposition technique uses separate sets of galaxy and quasar eigenspectra to efficiently and reliably separate the AGN and host spectroscopic components. The technique accurately reproduces the host galaxy spectrum, its contributing fraction, and its classification. We show how the accuracy of the decomposition depends upon S/N, host galaxy fraction, and …
We present the results of optical spectroscopic identifications of a bright subsample of 2-10keV hard X-ray selected sources from the ASCA Medium Sensitivity Survey in the northern sky. The flux limit of the subsample is 3*10^-13 erg s^-1 cm^-2 in the 2-10keV band. All but one of the 87 hard X-ray selected sources are optically identified, with AGNs, 7 clusters of galaxies, and 1 galactic star. It is the largest complete sample of hard X-ray selected AGNs at the bright flux limit. Amounts of absorption to their nuclei are estimated to be hydrogen column densities (N_H) of up to ~3*10^23 cm^-2 …
Because of the contamination of jets, using the size -- continuum luminosity relation can overestimate the broad line region (BLR) size and black hole mass for radio-loud AGNs. We propose a new relation between the BLR size and $H_β$ emission line luminosity and present evidences for using it to get more accurate black hole masses of radio-loud AGNs. For extremely radio-loud AGNs such as blazars with weak/absent emission lines, we suggest to use the fundamental plane relation of their elliptical host galaxies to estimate the central velocity dispersions and black hole masses, if their host gal…
We report the discovery of the scattered emission from a hidden broad-line region (BLR) in a Seyfert 2 galaxy, Mrk 573, based on our recent spectropolarimetric observation performed at the Subaru Telescope. This object has been regarded as a type 2 AGN without a hidden BLR by the previous observations. However, our high quality spectrum of the polarized flux of Mrk 573 shows prominent broad (~3000 km/s) H_alpha emission, broad weak H_beta emission, and subtle Fe II multiplet emission. Our new detection of these indications for the presence of the hidden BLR in the nucleus of Mrk 573 is thought…
The results of recent AGN monitoring campaigns confirm the ``big picture'' of the echo paradigm, but the details of the emission-line light curves cannot be accurately reproduced with only the simplest assumptions, some of which must be invalid. I discuss possible solutions. I present some preliminary optical light curves from Wise Observatory for NGC 4151 during the December 1993 multi-satellite campaign. The optical data show a continuity with the complex behavior observed in the IUE data, and may explain the peculiarities in emission-line response seen in this and other AGNs. I review some …
In order to investigate the connection between the X-ray, UV and optical spectral line regions, we selected a sample of AGN which have the strong Fe K-alpha line and analyze the UV and optical spectral lines. Here we present an example of AGN NGC 3516. In this object it seems that geometries of all three emitting regions are similar, i.e. the broad line shapes can be explained by the multicomponent emitting line region with a disk emission. The disk emission contributes to the wings, while one (spherical) emitting region contributes to the line core. Concerning the Fe K-alpha, UV and Balmer li…
We used the widths of H$β$ and [OIII] emission lines to investigate the black hole--bulge relation in radio-loud AGNs, radio-quiet AGNs and NLS1s. The central black hole mass, $M_{bh}$, is estimated from the H$β$ line width and the optical luminosity, and the bulge velocity dispersion, $σ$, is directly from the width of [OIII] line. We found that the radio-quiet AGNs follow the established $M_{bh}-σ$ relationship in nearby inactive galaxies, while the radio-loud AGNs and NLS1s deviate from this relationship. There are two plausible interpretations for the deviation of radio-loud AGNs. One is t…
More than one third of all nearby galaxies show indications of low-luminosity nuclear activity. These low-luminosity AGNs (LLAGNs) are traditionally classified into a variety of categories depending on their forbidden-line ratios and on the presence or absence of broad-line emission. By analogy with Seyfert unification models, it is natural to ask whether the various LLAGN types are different manifestations of the same underlying phenomenon, with observed differences being solely due to orientation and obscuration, or whether there are fundamentally distinct physical processes at work in diffe…
We present an X-ray spectral survey of radio-loud (RL) AGNs using ASCA and RXTE. The goal was to study the structure of their central engines and compare it to that of their radio-quiet (RQ) counterparts. We find Systematic differences in the X-ray properties of the two AGN classes. Specifically, RL AGNs exhibit weaker Fe lines and reflection components than RQ AGNs, indicating smaller solid angles subtended by the reprocessing medium to the X-ray source. The circumnuclear environs of RL and RQ AGNs also differ: large amounts of cold gas are detected in Broad Line Radio Galaxies and Quasars, c…
The nulling interferometers proposed to study planets around other stars are generally well suited for studying small-scale structures surrounding other bright pointlike objects such as the nuclei of active galaxies. Conventional interferometric techniques will produce useful maps of optical/IR line and continuum emission within active galaxies on scales of 10 milliarcseconds (mas), but similar studies of broad-line regions will require baselines longer than those currently envisaged. Nevertheless, nulling interferometers currently under development will be able to constrain quasar velocity fi…
The masses and emission-line region sizes of Active Galactic Nuclei (AGNs) can be measured by ``reverberation-mapping'' (measuring the lag of the emission-line luminosity after changes in the continuum). We use tis technique to calibrate similar size and mass estimates made by photoionization models of the AGN line-emitting regions. We compile a sample of 19 AGNs with reliable reverberation and spectroscopy data, twice the number available previously. The data provide strong evidence that the BLR size and the emission-line width measure directly the central mass. Two methods are used to estima…
An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which arise from the outer regions of the accretion disk which fuels the AGN. The line profiles vary on timescales of 5--10 years. Our group has monitored a set of 20 double-peaked emitters for the past 8 years (longer for some objects). Here we describe a project to characterize the variability patterns of the double-peaked H alpha line profiles and compare with those of two simple models: a circular disk with a spiral arm and an elliptical disk.
The results of spectropolarimetry surveys of obscured AGNs are reviewed, paying special attention to their implications for the existence of two populations of type 2 Seyfert galaxies -- hidden Seyfert 1s and "true" Seyfert 2s. In this context, the results from our Keck spectropolarimetry survey are presented. Similar to previous work, we have detected hidden broad-line regions (HBLRs) in about half of our sample. However, owing to different selection methods, we find that differences in the properties of HBLR and non-HBLR objects are much less pronounced than prior reports have indicated. Spe…
It is know that most of the clouds producing associated absorption in the spectra of AGNs and quasars do not completely cover the background source (continuum + broad emission line region, BLR). We note that the covering factor derived for the absorption is the fraction of photons occulted by the absorbing clouds, and is not necessarily the same as the fractional area covered. We show that the variability in absorption lines can be produced by the changes in the covering factor caused by the variation in the continuum and the finite light travel time across the BLR. We discuss how such a varia…
We reinvestigate the relationship between the characteristic broad-line region size (R_blr) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of R_blr for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of R_blr for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data sub-sample and regression technique. Though small systematic differences were found depending on the method of a…
In an examination of the relationship between the black hole mass and stellar velocity dispersion in radio-loud active galactic nuclei (AGNs), we studied two effects which may cause uncertainties in the black hole mass estimates of radio-loud AGNs: the relativistic beaming effect on the observed optical continuum radiation and the orientation effect on the broad emission line width. After correcting these two effects, we re-examined the relation between black hole mass and stellar velocity dispersion which derived from [OIII] line width for a sample of radio-loud and radio-quiet AGNs, and foun…
An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which are thought to arise from the outer regions of the accretion disk which fuels the AGN. The line profiles are observed to vary on a characteristic timescales of 5-10 years. The variability is not a reverberation effect; it is a manifestation of physical changes in the disk. Our group has monitored a set of 20 double-peaked emitters for the past 8 years (longer for some objects). Here, we characterize the variability of the double-peaked H alpha line profiles in five objects from our sample. By experimenting w…
Massive Black Holes detected in the centers of many nearby galaxies show an approximately linear relation with the luminosity of the host bulge, with the black hole mass being 0.001-0.002 of the bulge mass. Previous work suggested that black holes of active (Seyfert 1) galaxies follow a similar relation, but apparently with a significantly lower value of $M_{\rm BH}/M_{\rm bulge}$ (Wandel 1999). New data show that this difference was mainly due to overestimating the black hole mass in quiescent galaxies and overestimating the bulge magnitude of Seyfert galaxies. Using new and updated data we s…
It has been thought that narrow-line Seyfert 1 galaxies are likely to be in the early stages of the evolution of active galaxies. To test this suggestion, the ratios of the central massive black hole (MBH) mass to the bulge mass ($M_{\rm bh}/M_{\rm bulge}$) were estimated for 22 Narrow Line AGNs (NL AGNs). It is found that NL AGNs appear to have genuinely lower MBH/Bulge mass ratio ($M_{\rm bh}/M_{\rm bulge}$). The mean $ log(M_{\rm bh}/M_{\rm bulge})$ for 22 NL AGNs is $-3.9\pm 0.07$, which is an order of magnitude lower than that for Broad Line AGNs and quiescent galaxies. We suggest a nonli…
Based on the measured sizes of broad line region of the reverberation-mapping AGN sample, two new empirical relations are introduced to estimate the central black hole masses of radio-loud high-redshift ($z > 0.5$) AGNs. First, using the archival $IUE/HST$ spectroscopy data at UV band for the reverberation-mapping objects, we obtained two new empirical relations between the BLR size and \Mg/\C emission line luminosity. Secondly, using the newly determined black hole masses of the reverberation-mapping sample for calibration, two new relationships for determination of black hole mass with the f…
We report accurate redshifts of 110 active galaxies (mostly radio-loud objects at z<0.4) observed in the course of a survey to find broad, double-peaked emission lines. These redshifts are measured from the narrow emission lines of these objects and are accurate to at least one part in 10^4 . For each object we determine a redshift from high- and low-ionization lines separately, as well as an average redshift from all the available lines. We find that in about 15% of cases, the low-ionization lines yield a slightly higher redshift than the high-ionization lines; the average redshift difference…
