The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

Abstract

We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high-and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization Hα line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high-and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high-and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of Hα favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations.

Constraining the geometry and kinematics of the quasar broad emission line region using gravitational microlensing

“…Recent studies have shown that line profile distortions are commonly observed in gravitationally lensed quasar spectra (Richards et al 2004;Wayth et al 2005;Sluse et al 2007Sluse et al , 2011Sluse et al , 2012O'Dowd et al 2011;Guerras et al 2013;Braibant et al 2014Braibant et al , 2016Motta et al 2017). They are usually attributed to microlensing, that is, differential magnification of spatially and kinematically separated subregions of the broad emission line region (BLR).…”

Constraining the geometry and kinematics of the quasar broad emission line region using gravitational microlensing

“…Microlensing-induced line profile deformations are now commonly observed in gravitationally lensed quasar spectra, exhibiting various symmetric and asymmetric distortions in both low-and high-ionization line profiles (Richards et al 2004;Wayth et al 2005;Sluse et al 2007Sluse et al , 2011Sluse et al , 2012O'Dowd et al 2011;Guerras et al 2013;Braibant et al 2014Braibant et al , 2016. The size of the BLR has been estimated in a few objects and found compatible with reverberation mapping measurements (Wayth et al 2005;Sluse et al 2011;Guerras et al 2013).…”

“…In this paper, we extend those works, focusing on the interpretation of the observed line profile distortions caused by microlensing, such as those reported in Braibant et al (2014Braibant et al ( , 2016. The main purpose of our study is to determine whether simple BLR and microlensing models can reproduce the observations and then if it is possible to discriminate between the BLR models based on the observed microlensinginduced line profile distortions.…”

“…We describe our conclusions in the last section. In subsequent papers, models and simulations will be confronted to the observations reported in Braibant et al (2014Braibant et al ( , 2016 with the goal of constraining the geometry and kinematics of the BLR.…”

New Constraints on Quasar Broad Absorption and Emission Line Regions from Gravitational Microlensing

“…Making use of the MmD line profile disentangling technique, Braibant et al (2014Braibant et al ( , 2016 have extracted the part of the emission line profiles that is affected by microlensing in two lensed quasars for which high quality data were available. Fig.…”