Constraints for the accretion disk evaporation rate in AGN from the existence of the Broad Line Region

Abstract

Abstract.We analyze the consequences of the hypothesis that the formation of the Broad Line Region is intrinsically connected to the existence of the cold accretion disk. We assume that the Broad Line Region radius is reliably estimated by the formula of Kaspi et al. (2000, ApJ, 533, 631). We consider three models of the disappearance of the inner disk that limit the existence of the Broad Line Region: (i) the classical ADAF approach, i.e. the inner hot flow develops whenever it can exist; (ii) the disk evaporation model of Meyer & Meyer-Hofmeister (2002, A&A, 392, L5); (iii) the generalized disk evaporation model of Różańska & Czerny (2000b, A&A, 360, 1170. For each of the models, we determine the minimum value of the Eddington ratio and the maximum value of the broad line widths as functions of the viscosity parameter α and the magnetic field parameter β. We compare the predicted parameter space with observations of several AGN. Weak dependence of the maximum value of the FWHM and minimum value of the Eddington ratio on the black hole mass in our sample is noticeable. It seems to favor the description of the cold disk/hot inner flow transition as in the classical ADAF approach rather than with the model of disk evaporation due to conduction between the disk and accreting corona.

A Test of the Formation Mechanism of the Broad Line Region in Active Galactic Nuclei

“…If the existence of the BLR is tightly related to the presence of the underlying cold accretion disk, as frequently argued (e.g. Czerny et al 2004, Balmaverde & Capetti 2014, and the references therein), the significant change in the structure of the underlying disk should affect somehow the BLR. However, if the BLR lines form directly in the inflowing material (see Gaskell & Goosmann 2016) or come from the material temporarily ejected from the disk by passing stars (Zurek, Siemiginowska & Colgate 1994) then the physical state of the underlying disk becomes relatively unimportant.…”

The origin of the broad line region in active galactic nuclei

“…These studies have allowed several key properties of the BLR to be identified: (i) the emitting medium is located close to the accretion disk powering the AGN activity, and rarely crosses the line of sight towards the nucleus; (ii) the medium is predominantly in Keplerian motion with additional velocity components (e.g., Done & Krolik 1996;Kollatschny 2003;Collin et al 2006); (iii) the outer edge of the BLR is delineated by the dusty/molecular torus (Netzer & Laor 1993;Suganuma et al 2006); and (iv) the existence of BLR is likely to actually require the existence of the cold disk (e.g. Nicastro et al 2003;Czerny et al 2004;Cao 2010). However, major uncertainties about the geometry, dynamics, and physics of BLR still exist (for a review, see e.g.…”

The dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

“…The same conclusion was reached in recent statistical studies (e.g., Tommasin et al 2010;Wu et al 2011). Many authors argue that the lack of a broad line region (BLR) in the center of these Sy2 galaxies is luminosity and/or accretion rate dependent (Nicastro 2000;Lumsden & Alexander 2001;Gu & Huang 2002;Martocchia 2002;Panessa & Bassani 2002;Tran 2003;Nicastro et al 2003;Laor 2003;Czerny et al 2004;Elitzur & Shlosman 2006;Elitzur 2008;Elitzur & Ho 2009;Marinucci 2012;Elitzur et al 2014). Low luminosity can be the result of very low accretion rate and the BLR may possibly be absent in such systems.…”