We investigate the emission of active galactic nucleus (AGN) dusty tori in infrared domain. Following theoretical predictions derived from hydrodynamical simulations, we model the dusty torus as a 3D two-phase medium with high-density clumps and low-density medium filling the space between the clumps. Spectral energy distributions (SEDs) and images of the torus at different wavelengths are obtained using the 3D Monte Carlo radiative transfer code SKIRT. Our approach of generating clumpy structure allows us to model the tori with single clumps, complex structures of merged clumps or interconnected sponge-like structure. A corresponding set of clumps-only models and models with smooth dust distribution is calculated for comparison. We found that dust distribution, optical depth, clump size and their actual arrangement in the innermost region all have an impact on the shape of near-and mid-infrared SED. The 10-µm silicate feature can be suppressed for some parameters, but models with smooth dust distribution are also able to produce a wide range of silicate feature strength. Finally, we find that having the dust distributed in a two-phase medium might offer a natural solution to the lack of emission in near-infrared, compared to observed data, which affects clumpy models currently available in the literature.

We present a study of optical Fe II emission in 302 AGNs selected from the SDSS. We group the strongest Fe II multiplets into three groups according to the lower term of the transition (b 4 F , a 6 S and a 4 G terms). These correspond approximately to the blue, central, and red part respectively of the "iron shelf" around Hβ. We calculate an Fe II template which takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1. This Fe II template gives a more precise fit of the Fe II lines in broad-line AGNs than other templates. We extract Fe II, Hα, Hβ, [O III] and [N II] emission parameters and investigate correlations between them. We find that Fe II lines probably originate in an Intermediate Line Region. We notice that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM Hβ, the velocity shift of Fe II, and the Hα/Hβ flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of Fe II and [O III] on continuum luminosity. We find that there is a Baldwin effect for [O III] but an inverse Baldwin effect for the Fe II emission. The [O III]/Fe II ratio thus decreases with L λ5100 . Since the ratio is a major component of the Boroson and Green eigenvector 1, this implies a connection between the Baldwin effect and eigenvector 1, and could be connected with AGN evolution. We find that spectra are different for Hβ FWHMs greater and less than ∼3000 kms −1 , and that there are different correlation coefficients between the parameters.

Abstract. 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 Hβ and Hα 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 from ∼200 to 500 km s −1 and systematic velocities toward the blue from 20 to 350 km s −1 , and NLR2 with smaller random velocities (∼100−200 km s −1 ) and a redshift corresponding to the cosmological one. The BLR also have complex structure and we apply a two-component model assuming that the line wings originate in a very broad line region (VBLR) and the line core in an intermediate line region (ILR). The VBLR is assumed to be an accretion disk and the ILR a spherical emission region. The model fits very well the Hα and Hβ line profiles of the AGNs.

One of the most intriguing scenarios proposed to explain how active galactic nuclei are triggered involves the existence of a supermassive binary black hole system in their cores. Here we present an observational evidence for the first spectroscopically resolved sub-parsec orbit of a such system in the core of Seyfert galaxy NGC 4151. Using a method similar to those typically applied for spectroscopic binary stars we obtained radial velocity curves of the supermassive binary system, from which we calculated orbital elements and made estimates about the masses of components. Our analysis shows that periodic variations in the light and radial velocity curves can be accounted for an eccentric, sub-parsec Keplerian orbit of a 15.9-year period. The flux maximum in the lightcurve correspond to the approaching phase of a secondary component towards the observer. According to the obtained results we speculate that the periodic variations in the observed Hα line shape and flux are due to shock waves generated by the supersonic motion of the components through the surrounding medium. Given the large observational effort needed to reveal this spectroscopically resolved binary orbital motion we suggest that many such systems may exist in similar objects even if they are hard to find. Detecting more of them will provide us with insight into black hole mass growth process.

It is now agreed that mergers play an essential role in the evolution of galaxies and therefore that mergers of supermassive black holes (SMBHs) must have been common. We see the consequences of past supermassive binary black holes (SMBs) in the light profiles of so-called 'core ellipticals' and a small number of SMBs have been detected. However, the evolution of SMBs is poorly understood. Theory predicts that SMBs should spend a substantial amount of time orbiting at velocities of a few thousand kilometers per second. If the SMBs are surrounded by gas observational effects might be expected from accretion onto one or both of the SMBHs. This could result in a binary Active Galactic Nucleus (AGN) system. Like a single AGN, such a system would emit a broad band electromagnetic spectrum and broad and narrow emission lines.The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emit very broad and complex line profiles, showing two displaced peaks, one blueshifted and one redshifted from the systemic velocity defined by the narrow lines, or a single such peak. It has been proposed that such line shapes could indicate an SMB system. We discuss here how the presence of an SMB will affect the BLRs of AGNs and what the observational consequences might be.We review previous claims of SMBs based on broad line profiles and find that they may have non-SMB explanations as a consequence of a complex BLR structure. Because of these effects it is very hard to put limits on the number of SMBs from broad line profiles. It is still possible, however, that unusual broad line profiles in combination with other observational effects (line ratios, quasi-periodical oscillations, spectropolarimetry, etc.) could be used for SMBs detection.Some narrow lines (e.g., [O III]) in some AGNs show a double-peaked profile. Such profiles can be caused by streams in the Narrow Line Region (NLR), but may also indicate the presence of a kilo-parsec scale mergers. A few objects indicated as doublepeaked narrow line emitters are confirmed as kpc-scale margers, but double-peaked narrow line profiles are mostly caused by the complex NLR geometry.We briefly discuss the expected line profile of broad Fe Kα that probably originated in the accretion disk(s) around SMBs. This line may also be very complex and indicate the complex disk geometry or/and an SMB presence.Finally we consider rare configurations where a SMB system might be gravitationally lensed by a foreground galaxy, and discuss the expected line profiles in these systems.

We present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 Hβ spectra and analyzed the long-term spectral variations of the 5100Å continuum and the Hβ line. Our analysis is based on standard procedures, including the LombScargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a -2 -∼5700 day periodicity in the continuum light curve, the Hβ light curve, and the radial velocity curve of the red wing of the Hβ line. The data are consistent with orbital motion inside the broad emission line region of the source. We discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk.

Aims. Results of long-term spectral monitoring of the active galactic nucleus of NGC 4151 are presented (11 years, from 1996 to 2006). Methods. High quality spectra (S /N > 50 in the continuum near Hα and Hβ) were obtained in the spectral range ∼4000 to 7500 Å, with a resolution between 5 and 15 Å, using the 6-m and the 1-m SAO's telescopes (Russia), the GHAO's 2.1-m telescope (Cananea, México), and the OAN-SPM's 2.1-m telescope (San-Pedro, México). The observed fluxes of the Hα, Hβ, Hγ, and HeIIλ4686 emission lines and of the continuum at the observed wavelength 5117 Å were corrected for the position angle, the seeing, and the aperture effects. Results. We found that the continuum and line fluxes varied strongly (up to a factor 6) during the monitoring period. The emission was maximum in 1996−1998, and there were two minima in 2001 and in 2005. As a consequence, the spectral type of the nucleus changed from a Sy1.5 in the maximum activity state to a Sy1.8 in the minimum state. The Hα, Hγ, and Heλ4686 fluxes correlated well with the Hβ flux. The line profiles were strongly variable, showing changes of the blue and red asymmetry. The flux ratios of the blue/red wings and of the blue (or red) wing/core of Hα and Hβ varied differently. We considered three characteristic periods during which the Hβ and Hα profiles were similar : 1996−1999, 2000−2001, and 2002−2006. The line-to-continuum flux ratios were different; in particular during the first period (1996)(1997)(1998)(1999), the lines were not correlated with the continuum and saturated at high fluxes. In the second and third periods (2000)(2001)(2002)(2003)(2004)(2005)(2006), where the continuum flux was small, the Hα and Hβ fluxes were well correlated to the continuum flux, meaning that the ionizing continuum was a good extrapolation of the optical continuum. The CCFs are often asymmetrical and the time lags between the lines and the continuum are badly defined, indicating the presence of a complex BLR, with dimensions from 1 to 50 light-days. Conclusions. We discuss the different responses of Hβ and Hα to the continuum during the monitoring period.

Here we present the spectropolarimetric observations of a sample of 30 Type 1 AGNs and an analysis of the observed polarization in these AGNs. The observations have been performed with the 6-meter telescope of SAO RAS using the modified SCORPIO-2 spectropolarimeter. We measured the Stokes parameters for the continuum and the broad Hα line and obtained the values of polarization degree and the angle of polarization. We found that equatorial scattering is dominant polarization mechanism in the sample, that allows us to use the observed polarization in the broad lines for determination of the central black hole (BH) masses and characteristics (the inclination and emissivity) of the Broad Line Region (BLR). We demonstrated that the recently proposed method of for BH mass measurement gives accurate BH masses which are in a good correlation with the stellar velocity dispersion, and consequently the masses determined by the polarization method can be used with calibration purposes. Additionally we found that the BLR in the sample of 30 AGN has an averaged inclination of 35 • ± 9 • (mostly between 20 and 40 degrees) and emissivity α ∼ −0.57 that is more flat than one expected for the classical accretion disc α ∼ −0.75.