Gravitational microlensing of a reverberating quasar broad-line region - I. Method and qualitative results★

Abstract

The kinematics and morphology of the broad emission‐line region (BELR) of quasars are the subject of significant debate. The two leading methods for constraining BELR properties are microlensing and reverberation mapping. Here we combine these two methods with a study of the microlensing behaviour of the BELR in Q2237+0305, as a change in continuum emission (a ‘flare’) passes through it. Beginning with some generic models of the BELR – sphere, bicones, disc – we slice in velocity and time to produce brightness profiles of the BELR over the duration of the flare. These are numerically microlensed to determine whether microlensing of reverberation mapping provides new information about the properties of BELRs. We describe our method and show images of the models as they are flaring, and the unlensed and lensed spectra that are produced. Qualitative results and a discussion of the spectra are given in this paper, highlighting some effects that could be observed. Our conclusion is that the influence of microlensing, while not strong, can produce significant observable effects that will help in differentiating the properties of BELRs.

Microlensing of Quasar Broad Emission Lines: Constraints on Broad Line Region Size

“…The amplitude of the magnification is controlled by the size of the emission region, with smaller source regions showing larger magnifications. The broad line region was initially considered to be too large to be affected by microlensing (Nemiroff 1988, Schneider & Wambsganss 1990), but for sizes consistent with the reverberation mapping results the broad line regions should show microlensing variability (see Mosquera & Kochanek 2011) as explored in theoretical studies by Abajas et al (2002Abajas et al ( , 2007, Lewis & Ibata (2004) and Garsden et al (2011). Observational evidence for microlensing in the broad line region has been discussed for Q2237+0305 (Lewis et al 1998, Metcalf et al 2004, Wayth et al 2005, Eigenbrod et al 2008, O'Dowd et al 2010, Sluse et al 2011, SDSS J1004+4112 (Richards et al 2004, Gómez-Álvarez et al 2006, Lamer et al 2006, Abajas et al 2007) and SDSS J0924+0219 (Keeton et al 2006), as well as in broader surveys by Sluse et al (2012) and Motta et al (2012).…”

Gravitational microlensing of active galactic nuclei dusty tori

“…The ‘chromaticity’ in lensing effect can be used to investigate both an unresolved structure of the innermost region of quasars (see e.g. Abajas et al ; Wyithe, Agol & Fluke ; Popović et al , ; Bate et al ; Mosquera et al ; Dai et al ; Blackburne et al ; Garsden, Bate & Lewis ) and the structure of the lens galaxy (see e.g. Chiba et al ; Inoue & Chiba ; Xu et al ).…”

Microlensing of the broad line region in 17 lensed quasars

“…In the last decade, important progress in observational techniques allowed photometric and spectrophotometric monitoring of the individual lensed images to be successfully carried out (Woźniak et al 2000;Dai et al 2003;Anguita et al 2008b;Eigenbrod et al 2008;Zimmer et al 2011). On the other hand, the development of more advanced numerical techniques allowed quicker calculation of magnification maps and more sophisticated analysis (Kochanek 2004;Poindexter & Kochanek 2010a,b;Bate et al 2010;Mediavilla et al 2011;Garsden et al 2011;Bate & Fluke 2012). Owing to these two ingredients, tight constraints on the size of the accretion disc and on its temperature profile, on the size of the broad line region and on its kinematics have been obtained for Q2237+0305 (Eigenbrod et al 2008;Poindexter & Kochanek 2010a;O'Dowd et al 2011;Sluse et al 2011).…”