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تسجيل مستخدم جديدBLR size in Realistic FRADO Model: The role of shielding effect
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The effective size of Broad Line Region (BLR), so-called the BLR radius, in galaxies with active galactic nuclei (AGN) scales with the source luminosity. Therefore by determining this location either observationally through reverberation mapping or theoretically, one can use AGNs as an interesting laboratory to test cosmological models. In this article we focus on the theoretical side of BLR based on the Failed Radiatively Accelerated Dusty Outflow (FRADO) model. By simulating the dynamics of matter in BLR through a realistic model of radiation of accretion disk (AD) including the shielding effect, as well as incorporating the proper values of dust opacities, we investigate how the radial extension and geometrical height of the BLR depends on the Eddington ratio [and blackhole mass], and modeling of shielding effect. We show that assuming a range of Eddington ratios and shielding we are able to explain the measured time-delays in a sample of reverberation-measured AGNs.
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The dynamics of the Broad Line Region (BLR) in Active galaxies is an open question, direct observational constraints suggest a predominantly Keplerian motion, with possible traces of inflow or outflow. In this paper we study in detail the physically
motivated BLR model of (Czerny & Hryniewicz, 2011) based on the radiation pressure acting on dust at the surface layers of accretion disk (AD). We consider here a non-hydrodynamical approach to the dynamics of the dusty cloud under the influence of radiation coming from the entire AD. We use here the realistic description of the dust opacity, and we introduce two simple geometrical models of the local shielding of the dusty cloud. We show that the radiation pressure acting on dusty clouds is strong enough to lead to dynamical outflow from the AD surface, so the BLR has a dynamical character of (mostly failed) outflow. The dynamics strongly depend on the Eddington ratio of the source. Large Eddington ratio sources show a complex velocity field and large vertical velocities with respect to the AD surface, while for lower Eddington ratio sources vertical velocities are small and most of the emission originates close to the AD surface. Cloud dynamics thus determines the 3-D geometry of the BLR.
In Failed Radiatively Accelerated Dusty Outflow (FRADO) model which provides the source of material above the accretion disk (AD) as an option to explain the formation mechanism of Broad Line Region (BLR) in AGNs, the BLR inner radius ($rm{BLR}_{in}$
hereafter) is set by the condition that the dust evaporates immediately upon departure from the AD surface. On the other hand, the location of BLR clouds obtained observationaly via reverberation mapping shows some scaling with the source luminosity, so-called RL relation. We assume $rm{BLR}_{in}$ to be the location of BLR clouds, then using a realistic expression for the radiation pressure of an AD, and having included the proper values of dust opacity, and shielding effect as well, we report our numerical results on calculation of $rm{BLR}_{in}$ based on FRADO model. We investigate how it scales with monochromatic luminosity at 5100 angstrom for a grid of blackhole masses and Eddington ratios to compare along with the FRADO analytically predicted RL directly to observational data.
For a compiled sample of 120 reverberation-mapped AGNs, the bivariate correlations of the broad-line regions (BLRs) size ($R_{rm BLR}$) with the continuum luminosity at 5100 AA ($L_{5100}$) and the dimensionless accretion rates ($dot{mathscr{M}}$) ar
e investigated. Using our recently calibrated virial factor $f$, and the velocity tracer from the H$beta$ Full-width at half-maximum (FWHM(H$beta$)) or the line dispersion ($sigma_{rm Hbeta}$) measured in the mean spectra, three kinds of SMBH masses and $dot{mathscr{M}}$ are calculated. An extended RL relation including $dot{mathscr{M}}$ is found to be stronger than the canonical $R_{rm BLR}({rm Hbeta}) - L_{rm 5100}$ relation, showing smaller scatters. The observational parameters, $R_{rm Fe}$ (the ratio of optical Fe II to H$beta$ line flux) and the line profile parameter $D_{rm Hbeta}$ ($D_{rm Hbeta}=rm FWHM(Hbeta)/sigma_{rm Hbeta}$), have relations with three kinds of $dot{mathscr{M}}$. Using $R_{rm Fe}$ and $D_{rm Hbeta}$ to substitute $dot{mathscr{M}}$, extended empirical $R_{rm BLR}({rm Hbeta}) - L_{rm 5100}$ relations are presented. $R_{rm Fe}$ is a better fix for the $R_{rm BLR}({rm Hbeta}) - L_{rm 5100}$ offset than the H$beta$ shape $D_{rm Hbeta}$. The extended empirical $R_{rm BLR}({rm Hbeta}) - L_{rm 5100}$ relation including $R_{rm Fe}$ can be used to calculate $R_{rm BLR}$, and thus the single-epoch SMBH mass $M_{rm BH}$. Our measured accretion rate dependence is not consistent with the simple model of the accretion disk instability leading the BLRs formation. The BLR may instead form from the inner edge of the torus, or from some other means in which BLR size is positively correlated with accretion rate and the SMBH mass.
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