Microlensing of the broad emission lines in 27 gravitationally lensed quasars

Abstract

Aims. We aim to study the structure and kinematics of the broad line region (BLR) of a sample of 27 gravitationally lensed quasars with up to five different epochs of observation. This sample is composed of ∼100 spectra from the literature plus 22 unpublished spectra of 11 systems. Methods. We measure the magnitude differences in the broad emission line (BEL) wings and statistically model the distribution of microlensing magnifications to determine a maximum likelihood estimate for the sizes of the C IV, C III], and Mg II emitting regions. Results. The BELs in lensed quasars are expected to be magnified differently owing to the different sizes of the regions from which they originate. Focusing on the most common BELs in our spectra (C IV, C III], and Mg II), we find that the low-ionization line Mg II is only weakly affected by microlensing. In contrast, the high-ionization line C IV shows strong microlensing in some cases, indicating that its emission region is more compact. Thus, the BEL profiles are deformed differently depending on the geometry and kinematics of the corresponding emitting region. We detect microlensing in either the blue or the red wing (or in both wings with different amplitudes) of C IV in more than 50% of the systems and find outstanding asymmetries in the wings of QSO 0957+561, SDSS J1004+4112, SDSS J1206+4332, and SDSS J1339+1310. This observation indicates that the BLR is, in general, not spherically symmetric and supports the existence of two regions in the BLR, one insensitive to microlensing and another that only shows up when it is magnified by microlensing. Disregarding the existence of these two regions, our estimate for Mg II, R1/2 = 67.3−15.7+3.8 √(M/M⊙) light-days, is in good agreement with previous results from smaller samples, while we obtain smaller sizes for the C III] and CIV lines, R1/2 = 31.0−4.0+1.9 √(M/M⊙) light-days and R1/2 = 15.5−3.9+0.8 √(M/M⊙) light-days, respectively.

A Mass Model for the Lensing Cluster SDSS J1004+4112: Constraints from the Third Time Delay

“…However, there are still issues that remain unsolved like the origin of the enhanced asymmetric wings in the broad emission lines of quasar image A (Richards et al 2004;Gómez-Álvarez et al 2006;Lamer et al 2006;Motta et al 2012;Fian et al 2018;Popović 2020;Fian et al 2021).…”

Fast Multipole Method for Gravitational Lensing: Application to High-magnification Quasar Microlensing

“…The calculation of extragalactic gravitational microlensing magnification maps (e.g., Wambsganss 2006), which may involve a large number of deflectors and needs to map a huge number of rays, is probably one of the most computationally demanding examples. Gravitational microlensing of extragalactic sources allows one to obtain information on several aspects of lenses and sources that is difficult to obtain by different means (e.g., the abundance and mass of any kind of compact objects in the lens; the quasar structure at several scales, from the large torus (e.g., Popović et al 2020) and the broad-line region (BLR; e.g., Fian et al 2021 and references therein) down to the innermost regions of the accretion disk (e.g., Morgan et al 2010;Jiménez-Vicente et al 2012;Mediavilla et al 2015)). These studies are usually based on the estimate of the statistical likelihood of the observed magnification of the source for different values of the parameters of interest (abundance and mass of the microlenses, size and temperature profile of the source, etc).…”

“…These problems would therefore be difficult to address with preexisting codes without high-performance/ memory hardware and/or too-long execution times. Microlensing and millilensing affect the regions in which AGN and quasars are structured with different strengths depending on their size, from the smallest scales of the event horizon and the innermost stable circular orbit (ISCO; see Mediavilla et al 2015), through the intermediate scales of the accretion disk and BLR (e.g., Morgan et al 2010;Jiménez-Vicente et al 2012;Fian et al 2021), up to the large scale of the torus of scattered light (see Popović et al 2020). For singleepoch microlensing, as the intrinsic brightness of the source is unknown, a baseline defining zero microlensing is needed to measure the impact of microlensing magnification (e.g., Mediavilla et al 2009).…”

Discovering strongly lensed quasar candidates with catalogue-based methods from DESI Legacy Surveys

“…In addition to constraining the cosmological model, strong lensing time delay systems, typically multiply imaged lensed QSOs, provide valuable insight to astrophysical problems such as constraining distributions of dark and luminous matter of the lenses (Oguri et al 2014;Suyu et al 2014;Sonnenfeld & Cautun 2021;Van de Vyvere et al 2022), and uncovering the properties of distant active galactic nuclei (AGN) and their host galaxies to a level of detail not possible without lens magnification (e.g., McGreer et al 2010;More et al 2015;Fan et al 2019;Yue et al 2022). In the case of the latter, microlensing caused by small structures within the lens have revealed fine-level details of AGN morphology such as accretion disk characteristics (Anguita et al 2008;Motta et al 2012;Braibant et al 2014;Fian et al 2021).…”