The Interferometric Monitoring of Gamma–ray Bright Active galactic nuclei (iMOGABA) program provides not only simultaneous multifrequency observations of bright gamma–ray detected active galactic nuclei (AGN), but also covers the highest Very Large Baseline Interferometry (VLBI) frequencies ever being systematically monitored, up to 129 GHz. However, observation and imaging of weak sources at the highest observed frequencies is very challenging. In the second paper in this series, we evaluate the viability of the frequency phase transfer technique to iMOGABA in order to obtain larger coherence time at the higher frequencies of this program (86 and 129 GHz) and image additional sources that were not detected using standard techniques. We find that this method is applicable to the iMOGABA program even under non–optimal weather conditions.

Observations show that the accretion ows in low-luminosity active galactic nuclei (LLAGNs) probably have a two-component structure with an inner hot, optically thin, advection dominated accretion flow (ADAF) and an outer truncated cool, optically thick accretion disk. As shown by Taam et al. (2012), within the framework of the disk evaporation model, the truncation radius as a function of mass accretion rate is strongly affected by including the magnetic field. We define the parameter β as pm = B2=8π = (1 - β)ptot, (where ptot = pgas + pm, pgas is gas pressure and pm is magnetic pressure) to describe the strength of the magnetic field in accretion ows. It is found that an increase of the magnetic field (decreasing the value of β) results in a smaller truncation radius for the accretion disk. We calculate the emergent spectrum of an inner ADAF + an outer truncated accretion disk around a supermassive black hole by considering the effects of the magnetic field on the truncation radius of the accretion disk. By comparing with observations, we found that a weaker magnetic field (corresponding to a bigger value of β) is required to match the observed correlation between L2-10keV/LEdd and the bolometric correction K2-10keV, which is consistent with the physics of the accretion ow with a low mass accretion rate around a black hole.

We present a GUI-based interactive Python program, VIMAP, which generates radio spectral index maps of active galactic nuclei (AGN) from Very Long Baseline Interferometry (VLBI) maps obtained at different frequencies. VIMAP is a handy tool for the spectral analysis of synchrotron emission from AGN jets, specifically of spectral index distributions, turn-over frequencies, and core-shifts. In general, the required accurate image alignment is difficult to achieve because of a loss of absolute spatial coordinate information during VLBI data reduction (self-calibration) and/or intrinsic variations of source structure as function of frequency. These issues are overcome by VIMAP which in turn is based on the two-dimensional cross-correlation algorithm of Croke & Gabuzda (2008). In this paper, we briefly review the problem of aligning VLBI AGN maps, describe the workflow of VIMAP, and present an analysis of archival VLBI maps of the active nucleus 3C 120.

We present a test of the emission statistics of active galactic nuclei (AGN), probing the connection between red-noise temporal power spectra and multi-modal flux distributions known from observations. We simulate AGN lightcurves under the assumption of uniform stochastic emission processes for different power-law indices of their power spectra. For sufficiently shallow slopes (power-law indices β≤ 1), the flux distributions (histograms) of the resulting lightcurves are approximately Gaussian. For indices corresponding to steeper slopes (β≥ 1), the flux distributions become multi-modal. This finding disagrees systematically with results of recent mm/radio observations. Accordingly, we conclude that the emission from AGN does not necessarily originate from uniform stochastic processes even if their power spectra suggest this. Possible mechanisms are transitions between different activity states and/or the presence of multiple, spatially disconnected, emission regions.

We investigate the mid-infrared (MIR) to far-infrared (FIR) properties of a nearly complete sample of local active galactic nuclei (AGNs) detected in the Swift/Burst Alert telescope (BAT) all-sky hard X-ray (14-195 keV) survey, based on the cross correlation with the infrared survey catalogs of AKARI, IRAS and WISE. Out of 135 non-blazar AGNs in the Swift/BAT 9-month catalog, we obtain the MIR photometric data for 128 sources in either the 9, 12, 18, 22, and $25{\mu}m$ band. We find a good correlation between their hard X-ray and MIR luminosities ranging three orders of magnitude (42 < log λLλ(9,18 μm ) < 45), which is tighter than that with the FIR luminosities at 90 μm . Both X-ray unabsorbed and absorbed AGNs follow the same correlation, implying isotropic infrared emission, as expected in clumpy dust tori models rather than homogeneous ones.

Many observations have found evidence of the presence of a large number of heavily obscured Active Galactic Nuclei (AGNs). However, the nature of this population is only poorly understood because heavy obscuration by dust prevents one from finding them at optical wavelengths. Mid-infrared AGN searches can overcome this obstacle by penetrating through dust and by detecting direct emission from the dust torus. Thus, we can identify most of the AGN population, including type-2 and buried AGNs. Using the AKARI mid-infrared all-sky survey, we performed an AGN search in the nearby universe. Utilizing the 2MASS photometry, we selected mid-infrared-excess sources and carried out near-infrared spectroscopic observations in the AKARI Phase 3. During these follow-up observations, we have found three galaxies that show strong near-infrared red continuum from hot dust with a temperature of about 500 K, but do not show any AGN features in other wavelengths. The most suitable explanation of near-infrared continuum is the presence of central AGNs. Therefore, we conclude that they are AGNs obscured by dust. We performed X-ray observations of the two galaxies with SUZAKU. No detections in the 0.4-10 keV suggest that the column density may be much higher than NH=1023.5cm−2 . Comparing the masses of the host galaxies with those of the SDSS AGNs, we find that the host galaxies of the dusty AGNs discovered with AKARI are less massive populations than those of optically selected AGNs.

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with Δμ =0.1. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.