Microlensing of a Biconical Broad‐Line Region

Abajas, C.; Mediavilla, E.; Muñoz, J. A.; Gómez-Álvarez, P.; Gil-Merino, R.

doi:10.1086/511023

Cited by 35 publications

(42 citation statements)

References 37 publications

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“…Only one other system (HE 0047-1756) shows ML similar to the one observed in SDSS J0246-0825 but with a larger signal in one wing than in the other, a case which should in principle be more likely (Abajas et al 2002(Abajas et al , 2007. This might be an observational bias (microlensing of the other wing is too small to be detected), or not.…”

Section: Consequences For the Blrmentioning

confidence: 68%

“…This effect is expected for most of the BLR geometries studied in the literature when the source lies in a large demagnification valley of the micro-caustic network or when a large fraction of the source crosses a micro-caustic (e.g. Abajas et al 2007). In the first case the symmetry should last several crossing timescale 7 while in the second case, the effect should be more transient.…”

Section: Microlensing Of the Blrmentioning

confidence: 87%

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Microlensing of the broad line region in 17 lensed quasars

Sluse

Hutsemékers

Courbin

et al. 2012

A&A

133

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 This sample is composed of 13 pairs of previously unpublished spectra and four pairs of spectra from literature.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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Section: Consequences For the Blrmentioning

confidence: 68%

Section: Microlensing Of the Blrmentioning

confidence: 87%

Microlensing of the broad line region in 17 lensed quasars

Sluse

Hutsemékers

Courbin

et al. 2012

A&A

133

184

View full text Add to dashboard Cite

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“…The BLR was once considered too large to be affected significantly by microlensing. Studies have shown, however, that the BLR can be small enough to be amplified significantly by stellar-mass objects (Abajas et al 2007, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Spectral variability of quasars from multi-epoch photometric data in the Sloan Digital Sky Survey Stripe 82

Meusinger

Hinze

Hoon

2010

A&A

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Aims. The study of the ensemble properties of the UV/optical broadband variability of quasars is hampered by the combined effects of the dependence of variability on timescale, rest-frame wavelength, and luminosity. Here, we present a new approach to analysing the dependence of quasar variability on rest-frame wavelengths. Methods. We exploited the spectral archive of the Sloan Digital Sky Survey (SDSS) to create a sample of over 9000 quasars in the Stripe 82. The quasar catalogue was matched with the Light Motion Curve Catalogue for SDSS Stripe 82 and first-order structure functions were computed from the lightcurves. The structure functions are used to create a variability indicator that is related to the same intrinsic timescales for all quasars (about 1 to 2 yr in the rest-frame). We study the variability ratios for adjacent SDSS filter bands as a function of redshift. A quantitative interpretation of these relations is provided by comparing with the results of simple Monte Carlo simulations of variable quasar spectra. Results. We confirm the well-known dependence of variability on time-lag; the best power-law fit of the sample-averaged structure function has a slope β = 0.31 ± 0.03. We also confirm that anti-correlations exist with luminosity, wavelength, and redshift, where the latter can be fully explained as a consequence of the former two dependencies. The variability ratios as a function of redshift resemble the corresponding colour index-redshift relations. While variability is almost always stronger in the bluer passband than in the redder, the variability ratio depends on whether strong emission lines contribute to either one band or the other. We find that the observed variability ratio-redshift relations are described well assuming that (a) the r.m.s. fluctuation of the quasar continuum flux follows a power law σ( f λ ) ∝ λ −2 (i.e., is bluer when brighter) and (b) the variability of the emission line flux is only ∼10% of that of the underlying continuum. These results, based upon the photometry of more than 8000 quasars, confirm the previous findings by Wilhite and collaborators for 315 quasars with repeated SDSS spectroscopy. Finally, we find that quasars with unusual spectra and weak emission lines tend to have less variability than conventional quasars. This trend is the opposite of that expected from the dilution effect of variability due to line emission and may be indicative of high Eddington ratios in these unusual quasars.

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“…In a more detailed investigation, Lewis et al [48] showed that spectroscopic monitoring of multiple quasars can be used to probe the broad line regions (cf. also [1,2,9,49,51,71]). …”

Section: Theoretical Work On Quasar Microlensingmentioning

confidence: 97%

Quasar microlensing

Schmidt

Wambsganß

2010

Gen Relativ Gravit

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Quasar microlensing deals with the effect of compact objects along the line of sight on the apparent brightness of the background quasars. Due to the relative motion between quasar, lenses and observer, the microlensing magnification changes with time which results in uncorrelated brightness variations in the various images of multiple quasar systems. The amplitudes of the signal can be more than a magnitude with time scales of weeks to months to years. The effect is due to the "granular" nature of the gravitational microlenses-stars or other compact objects in the stellar mass range. Quasar microlensing allows to study the quasar accretion disk with a resolution of tens of microarcseconds, hence quasar microlensing can be used to explore an astrophysical field that is hardly accessible by any other means. Quasar microlensing can also be used to study the lensing objects in a statistical sense, their nature (compact or smoothly distributed, normal stars or dark matter) as well as transverse velocities. Quasar microlensing light curves are now being obtained from monitoring programs across the electromagnetic spectrum from the radio through the infrared and optical range to the X-ray regime. Recently, spectroscopic microlensing was successfully applied, it provides quantitative comparisons with quasar/accretion disk models. There are now more than a handful of systems with several-year long light curves and significant microlensing signal, lending to detailed analysis. This review summarizes the current state of the art of quasar microlensing and shows that at this point in time, observational monitoring programs and complementary intense simulations provide a scenario where some of the early promises of quasar microlensing can

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Microlensing of a Biconical Broad‐Line Region

Cited by 35 publications

References 37 publications

Microlensing of the broad line region in 17 lensed quasars

Microlensing of the broad line region in 17 lensed quasars

Spectral variability of quasars from multi-epoch photometric data in the Sloan Digital Sky Survey Stripe 82

Quasar microlensing

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