The Influence of Gravitational Microlensing on the Broad Emission Lines of Quasars

Abajas, C.; Mediavilla, E.; Muñoz, J. A.; Popovic, L. C.; Oscoz, A.

doi:10.1086/341793

Cited by 95 publications

(145 citation statements)

References 26 publications

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“…As microlensing is capable of selectively amplifying different regions depending on their size, it is possible that spectra in the active states are deformed in a complex manner [45,46] unrelated to General relativistic and reprocessing effects from the inner accretion disk [7]. As such, in this section we begin by co-adding the spectra and responses of Images-B and C to form two time-averaged spectra representative of the microlensing "quiet" state.…”

Section: Combined "Microlensing-quiet" Images-b and Cmentioning

confidence: 99%

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Reis

Reynolds

Miller

et al. 2014

Nature

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The co-evolution of a supermassive black hole with its host galaxy[1] through cosmic time is encoded in its spin[2, 3, 4]. At z > 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. However, it is unknown whether below z ∼ 1 these black holes continue to grow via coherent accretion or in a chaotic manner [5], though clear differences are predicted [3,4] in their spin evolution. An established method[6] to measure the spin of black holes is via the study of relativistic reflection features [7] from the inner accretion disk. Owing to their greater distances, there has hitherto been no significant detection of relativistic reflection features in a moderateredshift quasar. Here, we use archival data together with a new, deep observation of a gravitationally-lensed quasar at z = 0.658 to rigorously detect and study reflection in this moderate-redshift quasar. The level of relativistic distortion present in this reflection spectrum enables us to constrain the emission to originate within 3 gravitational radii from the black hole, implying a spin parameter a = 0.87 +0.08 −0.15 at the 3σ level of confidence and a > 0.66 at the 5σ level. The high spin found here is indicative of growth via coherent accretion for this black hole, and suggests that black hole growth between 0.5 z 1 occurs principally by coherent rather than chaotic accretion episodes. 1When optically-thick material, e.g. an accretion disc, is irradiated by hard X-rays, some of the flux is reprocessed into an additional 'reflected' emission component, which contains both continuum emission and atomic features. The most prominent signature of reflection from the inner accretion disc is typically the relativistic iron Kα line (6.4-6.97 keV; rest frame) [8] and the Compton reflection hump [7] often peaking at 20 − 30 keV (rest-frame). However, the deep gravitational potential and strong Doppler shifts associated with regions around black holes will also cause the forest of soft X-ray emission lines in the ∼ 0.7 − 2.0 keV range to be blended into a smooth emission feature, providing a natural explanation for the "soft-excess" observed in the X-ray spectra of nearby active galactic nuclei (AGNs) [9,10]. Indeed, both the iron line and the soft excess can be used to provide insight into the nature of the central black hole and to measure its spin [10]. Prior studies have revealed the presence of a soft-excess in 90% of quasars at[11, 12] z 1.7, and broad Fe-lines are also seen in 25% of these objects [11,13], suggesting that reflection is also prevalent in these distant AGNs. However, due to the inadequate S/N resulting from their greater distances, the X-ray spectra of these quasars were necessarily modeled using simple phenomenological parameterizations [12,14].Gravitational lensing offers a rare opportunity to study the innermost relativistic region in distant quasars [15,16], by acting as a natural telescope and magnifying the light from these sources. Quasars located between 0.5 z 1 are considerably ...

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Section: Combined "Microlensing-quiet" Images-b and Cmentioning

confidence: 99%

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Reis

Reynolds

Miller

et al. 2014

Nature

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“…In some cases, micro/milli-lensing can also modify the profiles of the BELs (e.g. Abajas et al 2002). The ratio between individual spectra thus provides one with a simple diagnostic of the presence of differential extinction or micro-lensing.…”

Section: Spectrum Ratiosmentioning

confidence: 99%

“…However, in order to discriminate between different BLR emission models, multi-epoch data as well as a realistic modelling of the BLR (e.g. Abajas et al 2002;Lewis & Ibata 2004) are necessary. This will be investigated in a future paper.…”

Section: Microlensing Of the Emission Line Regionsmentioning

confidence: 99%

“…In the present paper, we take advantage of long slit spectroscopy of J1131 to further study micro-lensing in this system and phenomenologically describe its effect on different emitting regions and in particular on the broad line emitting region (BLR). Abajas et al (2002) have shown, using the Kaspi et al (2000) relation linking the BLR size to the quasar luminosity, that the BLR of less luminous quasars is likely small enough (i.e. a few micro-arcseconds) to be affected by micro-lensing.…”

Section: Introductionmentioning

confidence: 99%

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Multi-wavelength study of the gravitational lens system RXS J1131-1231

Sluse

Claeskens

Hutsemékers

et al. 2007

A&A

108

114

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Aims. We discuss and characterize micro-lensing among the 3 brightest lensed images (A-B-C) of the gravitational lens system RXS J1131-1231 (a quadruply imaged AGN) by means of long slit optical and NIR spectroscopy. Qualitative constraints on the size of different emission regions are derived. We also perform a spectroscopic study of two field galaxies located within 1.6 arcmin radius from the lens. Methods. We decompose the spectra into their individual emission components using a multi-component fitting approach. A complementary decomposition of the spectra enables us to isolate the macro-lensed fraction of the spectra independently of any spectral modelling.Results. 1. The data support micro-lensing de-amplification of images A and C. Not only is the continuum emission microlensed in those images but also a fraction of the Broad Line emitting Region (BLR).2. Micro-lensing of a very broad component of Mg ii emission line suggests that the corresponding emission occurs in a region more compact than the other components of the emission line.3. We find evidence that a large fraction of the Fe ii emission arises in the outer parts of the BLR. We also find a very compact emitting region in the ranges 3080-3540 Å and 4630-4800 Å that is likely associated with Fe ii. 4. The [O iii] narrow emission line regions are partly spatially resolved. This enables us to put a lower limit of ∼110h −1 pc on their intrinsic size.5. Analysis of Mg ii absorption found in the spectra indicates that the absorbing medium is intrinsic to the quasar, has a covering factor of 20%, and is constituted of small clouds homogeneously distributed in front of the continuum and BLRs. 6. Two neighbour galaxies are detected at redshifts z = 0.10 and z = 0.289. These galaxies are possible members of galaxy groups reported at those redshifts.

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“…Despite these promising results, detection of microlensing in the emission lines remained elusive (Filippenko 1989; or invoked A&A 544, A62 (2012) to explain differences between the spectra of candidate lensed quasars (Steidel & Sargent 1991;Small et al 1997). The interest in BLR microlensing got revived with the papers of Abajas et al (2002) and of Lewis & Ibata (2004), who re-investigated this question after the discovery that the BLR was smaller than previously thought (Wandel et al 1999;Kaspi et al 2000). Based on the size of the BLR measured in NGC 5548 and using the scaling relation R BLR ∝ L 0.7 , Abajas et al (2002) estimated that the BLR should be significantly microlensed in about ∼30% of the systems.…”

Section: Introductionmentioning

confidence: 99%

Microlensing of the broad line region in 17 lensed quasars

Sluse

Hutsemékers

Courbin

et al. 2012

A&A

137

184

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When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting region. Chromatic changes are expected to be observed in the continuum while the emission lines should be deformed as a function of the size, geometry and kinematics of the regions from which they originate. Microlensing of the emission lines has been reported only in a handful of systems so far. In this paper we search for microlensing deformations of the optical spectra of pairs of images in 17 lensed quasars with bolometric luminosities between 10 44.7−47.4 erg/s and black hole masses 10 7.6−9.8 M . This sample is composed of 13 pairs of previously unpublished spectra and four pairs of spectra from literature. Our analysis is based on a simple spectral decomposition technique which allows us to isolate the microlensed fraction of the flux independently of a detailed modeling of the quasar emission lines. Using this technique, we detect microlensing of the continuum in 85% of the systems. Among them, 80% show microlensing of the broad emission lines. Focusing on the most common emission lines in our spectra (C iii] and Mg ii) we detect microlensing of either the blue or the red wing, or of both wings with the same amplitude. This observation implies that the broad line region is not in general spherically symmetric. In addition, the frequent detection of microlensing of the blue and red wings independently but not simultaneously with a different amplitude, does not support existing microlensing simulations of a biconical outflow. Our analysis also provides the intrinsic flux ratio between the lensed images and the magnitude of the microlensing affecting the continuum. These two quantities are particularly relevant for the determination of the fraction of matter in clumpy form in galaxies and for the detection of dark matter substructures via the identification of flux ratio anomalies.

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The Influence of Gravitational Microlensing on the Broad Emission Lines of Quasars

Cited by 95 publications

References 26 publications

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Multi-wavelength study of the gravitational lens system RXS J1131-1231

Microlensing of the broad line region in 17 lensed quasars

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